Before Daenerys returns from the Dothraki Sea, there will likely be a major power vacuum left after the end of the Battle of Fire.

The Competing Agendas of the Victors of the Battle of Fire

Note: We can argue about it in the comments, but I don't think there is much chance for the Slaver Alliance in the Battle of Fire. That said, that doesn't mean I don't think bad things will happen.

Note II: Its definitely possible that Dany/Drogon and the Dothraki arrive right at the end all deus ex machina, but (at least to me) it seems unnecessary and "off" (Drogon just showed up in Meereen in the same way in ADWD), etc. etc.

Background

With Dany gone, Hizdahr ruled as king until he was removed by Barristan who has started to "play the game of thrones". The Winds of Winter is going to "open with two huge battles" that will intercut back and forth according to GRRM (the Battles of Ice/Fire that were moved from the end of ADWD).

If interested: The Two Four Major Battles Opening The Winds of Winter

POV's in the Area: Barristan, Tyrion, Victarion

• Barristan is leading the charge against the trebuchets while the Unsullied form up, after convincing the Windblown to come over to Daenerys' side in exchange for Pentos
• Tyrion has helped the Second Sons flip to Daenerys side as well
• Victarion has the Ironborn attacking the ships of the Slaver's Alliance in the Bay

Something is Going to go Wrong

Its too "neat" of a situation (everything is going right for the good guys (unless you are fan of the Slaver's Alliance), but the SA just seems too inept to mount a strong enough comeback. As compared to the Battle of Ice where Stannis is looking to be in dire straights, but will likely win (or at least survive), the Attack on Storm's End (where the Golden Company plans to use some treachery) and the Battle of Blood (which seems like more of a sacrifice).

I expect twists and turns in each of these storylines, but what goes wrong (at least to me) will likely be issues with our victors and not some twist of fate and competency by the Slaver Alliance.

The Agendas

Barristan

Loyal to Daenerys (although theorized to turn to Young Griff), Barristan has started to scheme and play the game by removing a king and using political maneuvers (riding Dany's silver to battle) for inspiration.

PS: I need his Lads to survive.

Victarion (and the Iron Fleet)

Has been sent by Euron to claim Dany for him, but Victarion has his own agenda. He wants Dany and seemingly moreso (his focus seems to shift after he brings out the horn), a dragon.

The Tattered Prince (and the Windblown)

The leader of the Windblown, there is bound to be some conflict at some point, as the Tattered Prince has been promised Pentos by Barristan.

Moqorro

Has been sent by Benerro to bring the Lord of Light to Daenerys.

If interested: Moqorro's Visions or The Path Back to Westeros: Volantis

Marwyn

His past is so mysterious (so is his agenda) but he claims to be going to Meereen to aid Dany in Maester Aemon's place

All Aboard!: The Journey of the Cinnamon Wind

The Citadel's Man

The Citadel has possibly sent their own man to Slaver's Bay:

"What will you do?" asked Alleras, the Sphinx.
"Get myself to Slaver's Bay, in Aemon's place. The swan ship that delivered Slayer should serve my needs well enough. The grey sheep will send their man on a galley, I don't doubt. With fair winds I should reach her first."

If interested: "Others Seek Daenerys Too": The Citadel's Man

Brown Ben Plumm (and the Second Sons)

They have switched sides (back to Daenerys) again. That said they may prove instrumental in freeing the hostages (Daario, Hero, Jhogo) from the Slaver's Alliance.

The Elite of Meereen

The Green Grace, imprisoned Hizdahr/possibly Reznak, etc. along with the Harpy and the Sons of the Harpy.

The Dornishmen

Gerris Drinkwater and Arch Yronwood have been spared by Barristan and it implies that they might take the Demon Road back to Volantis.

Daario

Currently a prisoner of the Slaver's Alliance, he is a wildcard and has grown completely reckless since Dany's wedding.

The Unsullied

Allied to Dany. They will "obey".

Tyrion

Sworn his sword to the Second Sons. He is expected to spend most of the The Winds of Winter "apart" from Dany.

Dusky Woman

Euron's gifts are "poisoned". But Victarion has never managed to get around to killing her. She isn't a fan of Moqorro.

Jorah

Joined the Second Sons with Tyrion (and kind of Penny). He wants back in Dany's good graces as well.

There are numerous other small characters that could have an effect on the plot, as well as items, dragons and potentially attempts to ride them.

As I mentioned above, its possible that Dany arrives right as the battle is ending and restores order, but I find this unlikely (especially since Tyrion/Dany spend most of the book apart).

TLDR: While I think its likely that the loose alliance that is "Team Dany" will face some internal contention in the time after the battle and Dany's return and the longer that lasts, the more likely it is for something to go wrong.