Of the men sent to Slaver's Bay with poor Quentyn, only two are left alive of the original six:

If Prince Doran meant to send you into the middle of a battle, he would have given you three hundred knights, not three.”

Do not be so certain of that, ser. He sent my brother off to Slaver’s Bay with five knights and a maester*.* -TWOW, Arianne II

and:

Her father plucked up a cyvasse piece. "I must know how you learned that Quentyn was abroad. Your brother went with Cletus Yronwood, Maester Kedry, and three of Lord Yronwood's best young knights on a long and perilous voyage, with an uncertain welcome at its end. -AFFC, The Princess in the Tower

In this post I would like to discuss Gerris Drinkwater And Archbald Yronwood and their involvement in the story going forward.

Archibald Yronwood & Gerris Drinkwater: Returning to Dorne

As we know, Quentyn hires sellswords/attempts to ride a dragon, but before that numerous other members of their party died:

"Fuck your lineage," said Gerris. "The dragons won't care about your blood, except maybe how it tastes. You cannot tame a dragon with a history lesson. They're monsters, not maesters. Quent, is this truly what you want to do?"

"This is what I have to do. For Dorne. For my father. For Cletus and Will and Maester Kedry."

"They're dead," said Gerris. "They won't care."-ADWD, The Spurned Suitor

Characters

I don't think its too important to get into each character's background (feel free to discuss in the comments) outside of a few notes:

Ser Archbald Yronwood aka Greenguts aka The Big Man aka Arch

• An extremely large guy and seemingly good fighter/more intelligent than he looks who gets seasick extremely easily
• He is the newphew of Lord Anders Yronwood of Yronwood (where Quentyn was fostered due to the blood debt owed House Yronwood due to Oberyn):

Quentyn had been very young when he was sent to Yronwood; too young, according to their mother. Norvoshi did not foster out their children, and Lady Mellario had never forgiven Prince Doran for taking her son away from her. "I like it no more than you do," Arianne had overheard her father say, "but there is a blood debt, and Quentyn is the only coin Lord Ormond will accept." -AFFC, The Queenmaker

Ser Gerris Drinkwater aka Drink

• Good looking but not "worth all that much" according to Barristan:

Behind the prince, Ser Gerris Drinkwater was whispering something to Yronwood. Ser Gerris was all his prince was not: tall and lean and comely, with a swordsman's grace and a courtier's wit. Selmy did not doubt that many a Dornish maiden had run her fingers through that sun-streaked hair and kissed that teasing smile off his lips. If this one had been the prince, things might have gone elsewise, he could not help but think … but there was something a bit too pleasant about Drinkwater for his taste. False coin, the old knight thought. He had known such men before. -ADWD, The Discarded Knight

and:

"I feared as much." Neither enchanted nor enchanting, alas. A pity he's the prince, and not the one with the wide shoulders and the sandy hair. "You have come for a kiss, however. You mean to marry me. Is that the way of it? The gift you bring me is your own sweet self. Instead of Viserys and your sister, you and I must seal this pact if I want Dorne." -ADWD, Daenerys VII

Deal with Barristan

After Quentyn dies/the Dragon are released, the Dornishmen are imprisoned:

"And the other Dornish?" asked Tal Taraq.

"Prisoners, for the nonce." Neither of the Dornishmen had offered any resistance. Archibald Yronwood had been cradling his prince's scorched and smoking body when the Brazen Beasts had found him, as his burned hands could testify. He had used them to beat out the flames that had engulfed Quentyn Martell. Gerris Drinkwater was standing over them with sword in hand, but he had dropped the blade the moment the locusts had appeared. "They share a cell."

"Let them share a gibbet," said Symon Stripeback. "They unleashed two dragons on the city." -ADWD, The Queen's Hand

But Barry takes a couple of his lads to with him and negotiates with them:

Ser Barristan took two of his new-made knights with him down into the dungeons. Grief and guilt had been known to drive good men into madness, and Archibald Yronwood and Gerris Drinkwater had both played roles in their friend's demise. But when they reached the cell, he told Tum and the Red Lamb to wait outside whilst he went in to tell the Dornish that the prince's agony was over.

They discuss the rashness of Quentyn's actions (I will get to that) but then make a deal with Barry:

"Pentos," said Ser Barristan. "He promised him Pentos. Say it. No words of yours can help or harm Prince Quentyn now."

Aye," said Ser Archibald unhappily. "It was Pentos. They made marks on a paper, the two of them."

There is a chance here. "We still have Windblown in the dungeons. Those feigned deserters."

and:

"I mean to send them back to the Tattered Prince. And you with them. You will be two amongst thousands. Your presence in the Yunkish camps should pass unnoticed. I want you to deliver a message to the Tattered Prince. Tell him that I sent you, that I speak with the queen's voice. Tell him that we'll pay his price if he delivers us our hostages, unharmed and whole."

If we look at the issues in Slaver's Bay, one of them is that Hero, Jhogo and Daario are still help captive, but that the Second Sons seem like they could help free these hostages as well.

This is an issue because some of Dany's allies are in Pentos: The Path Back to Westeros: Conflict in/over Pentos

The Dornish Return "Plan"

Since Quentyn can no longer marry Daenerys, the Dornish Plan will be altered. I've argued that it will be extremely unlikely that Dorne will ally itself with Dany after word of what happened reaches Dorne. Im sure rumors, potential men Dorne sends after them, etc. will reach Dorne somewhat soon, but once/if Gerris/Arch return they are going to remind Dorne that "Fire & Blood" doesn't just mean vengeance, it means death/destruction everywhere.

Especially since it seems like Gerris will blame Daenerys for it all:

Ser Archibald, the big bald one, had nothing to say. He sat on the edge of his pallet, staring down at his bandaged hands in their linen wrappings. Ser Gerris punched a wall. "I told him it was folly. I begged him to go home. Your bitch of a queen had no use for him, any man could see that. He crossed the world to offer her his love and fealty, and she laughed in his face."

She never laughed," said Selmy. "If you knew her, you would know that."

If interested: Doran Martell: "Where is my Son?

So the Dornish will be returning Quentyn's bones home in return for assisting Barristan in getting the Windblown to switch sides:

"No." This one may not be as slow-witted as he seems. "I have more use for you alive than dead. Serve me, and afterward I will arrange a ship to take you back to Dorne and give you Prince Quentyn's bones to return to his lord father."

The Winds of Winter

It seems the ploy has worked and the Windblown have indeed switched sides:

The White Bull would have called it folly. He would have warned Barristan against trusting sellswords too. This is what it has come to, my queen, Ser Barristan thought. Our fates hinge upon a sellsword’s greed. Your city, your people, our lives … the Tattered Prince holds us all in his bloodstained hands**.** -TWOW, Barristan I

and:

“Gorzhak zo Eraz lies slain, cut down by Pentoshi treachery. The turncloak who names himself the Prince of Tatters shall die screaming for this infamy, the noble Morghar swears.” Brown Ben scratched at his beard. “The Windblown have gone over, have they?” he said, in a tone of mild interest. -TWOW, Tyrion I

Their Return Path

GRRM won't shut up about Archibald and ships. Its mentioned so many times. This leads me to believe that either a)something happens on a ship involving his seasickness or b) Gerris and Arch (and potentially the Windblown) march overland.

Arch was sick on the way over:

"Perhaps the big man is right," Ser Gerris said. "Piss on the sea, we can finish the journey overland."

"You know why he says that," Quentyn said. "He'd rather die than set foot on another ship." The big man had been greensick every day of their voyage. In Lys, it had taken him four days to recover his strength. They'd had to take rooms in an inn so Maester Kedry could tuck him into a feather bed and feed him broths and potions until some pink returned to his cheeks. -ADWD, The Merchant's Man

and their original return plan was a ship:

"Rags arranged for a ship," said Yronwood. "A big one, in case we got both dragons. And Quent was going to ride one." -ADWD, The Queensguard

and then the immediate response to Barristan's request:

Ser Archibald grimaced. "Why is it always ships? Someone needs to take Quent home, though. What do you ask of us, ser?" -ADWD, The Queen's Hand

and then the agreement:

Ser Archibald grimaced. "Rags and Tatters is more like to give the two of us to Pretty Meris. He won't do it."

"I'll do it," offered Ser Archibald, "just so long as there's no bloody boats involved. Drink will do it too." He grinned. "He don't know it yet, but he will."

As I mentioned they could march overland instead:

It was possible to go overland to Meereen, that much was true. The old Valyrian roads would take them there. Dragon roads, men called the great stone roadways of the Freehold, but the one that ran eastward from Volantis to Meereen had earned a more sinister name: the demon road. -ADWD, The Merchant's Man

If interested: The Path Back to Westeros: The Demon Road

TLDR: Once of the nuances of the Slaver's Bay plotline is the remaining Dornishmen. Not only is what they say to Dorne/Doran important, but they have also seemingly rejoined the Windblown (who have switched back to Dany and been promised Pentos) but also will be given Quentyn's bones.