The End of Tommen I's Reign

"I thought the crossbow fitting. You shared so much with Lord Tywin, why not that? Your niece will think the Tyrells had you murdered, mayhaps with the connivance of the Imp. The Tyrells will suspect her. Someone somewhere will find a way to blame the Dornishmen. Doubt, division, and mistrust will eat the very ground beneath your boy king, whilst Aegon raises his banner above Storm's End and the lords of the realm gather round him." -ADWD, Epilogue

I thought it would be fun to discuss the end of Tommen's reign (as we should probably expect it to come to an end somewhat quickly.

Background

Unlike his brother Joffrey, (who likely abused him), Tommen is a good little lad:

Tommen was a good-hearted little man who always tried his best

and he is easily one of the more adorable/innocent aspects of ASOIAF:

Tommen ran along, but before he left he turned back to say, "When I'm king in my own right, I'm going to outlaw beets."

and his interaction with "the bad cat" (aka Balerion):

The king seemed happier than Kevan Lannister had seen him in a long time. From soup to sweet Tommen burbled about the exploits of his kittens, whilst feeding them morsels of pike off his own royal plate. "The bad cat was outside my window last night," he informed Kevan at one point, "but Ser Pounce hissed at him and he ran off across the roofs."

"The bad cat?" Ser Kevan said, amused. He is a sweet boy.

that said, not only should we expect multiple people to sit the Iron Throne before the end of the series:

I know who's gonna be on the throne in the end. I'd better not say. There'll be a few people sitting on it before the answer. -SSM, Emmy Panel: March 2013

as well as potential foreshadowing (including the show, not saying it happens the same way), that he will be crowned and die:

The old woman was not done with her, however. "Gold shall be their crowns and gold their shrouds," she said. "And when your tears have drowned you, the valonqar shall wrap his hands about your pale white throat and choke the life from you." -AFFC, Cersei VIII

The Catalyst: Kevan's Death

Kevan's death is going to sow seeds of mistrust (as Varys) intended between the fragile Lannister/Tyrell alliance which is already frayed due to Cersei/Margaery.

If interested: The Current Situation in King's Landing

The Kinsguard

I posted about the potential divisions in the kingsguard a couple days ago. The point is that outside of Meryn Trant, each one of the kingsguard have reasons to be "disloyal" to the Lannisters (even Jaime in some ways).

The Tyrells

Tommen's marriage to Margaery (remember an unconsummated marriage can be set aside by the High Septon or a Council of the Faith) is what hold's the Lannister/Tyrell alliance together. If we look at the Tyrell's in King's Landing they are grasping for power (split Small Council, etc.).

The Faith

While the Faith has confirmed Tommen (in return for being rearmed), there is the pending trial of Cersei Lannister that should really affect the relationship. The use of Ser Robert Strong may offend the Faith (but to the best of our current knowledge, she likely wins her trial).

The Dornish

The Dornish have a party en route to King's Landing that includes Myrcella and two of the Sand Snakes.

Young Griff

At some point its very possible (even likely) that Young Griff takes King's Landing and is crowned King Aegon VI. This would require Tommen's death or at least disposal (say to Casterly Rock).

Note: We have other factors (Cersei's paranoia), Euron, Dany's arrival as well but I just wanted to point out the different factions in/around King's Landing who could lead to Tommen's downfall.

TLDR: While Tommen is a great kid and quite adorable, there are too many factions working against his reign (due to no fault of his) and his reign should be rather short. Poor Tommen.