What will be Tommen and Myrcella's fate's?

[King Adrian Storm]

Gold will be their crown's and gold will be their shrouds. We know at some point they will both be crowned, and both be killed. But how?

Tommen is already King so he has his crown, and Twow willl probably have him killed by Aegon or someone of the sort. His fate isn't too hard to figure out, but what about Myrcella? She's in Dorne, and Doran is planning on having Arianne wedded to Aegon, so how will she be crowned?

I think when Aegon invades Cersei will flee to Casterly rock, which we have been promised to see at some point in the story. Cersei will take Myrcella and Crown her Queen in the West, like Robb was King in the North. This would be a great explanation as to how Myrcella could be crowned, when so much is going on in King's landing. At some point Myrcella will die, who knows how, but it will most likely be Cersei's fault, and further her madness.

[Lord Daedrunk]

1 hour ago, King Adrian Storm said:

Gold will be their crown's and gold will be their shrouds. We know at some point they will both be crowned, and both be killed. But how?

'Gold will be their crown' could also refer to the very "curious" color of their hair, and not necessarily that each child will be a crowned regent. It's possible that Myrcella will be crowned at some point, however briefly, but it's also equally possible that she is not. 

But to get back to your main question of what their fates may be, I bet Myrcella will probably be killed by the sandsnakes in Dorne and Tommen probably by Varys or by suicide.   

[Willam Stark]

Totally agree ! Tommen will die at KL, and Myrcella will be crowned at Casterly Rock and die in Westerlands. 

No idea how, but I'm pretty sure they will die in those locations.

[Curled Finger]

Ser Pounce will smother Tommen in his sleep or choke him with turnips.  I thought Myrcella left Dorne and someone plans to have her kinapped or murdered there?  All that crossing and double crossing of Doran and Cersei and frickin Arianne makes my head spin.   Nonetheless, Myrcella will meet her maker in the woods on her way home.   Ick. 

[The Map Guy]

1 hour ago, Curled Finger said:

Ser Pounce will smother Tommen in his sleep or choke him with turnips.

Lol I love Ser Pounce theories

But Tommen will be pounced upon ... and then either be eaten or burned alive! Dracarys!!

Tommen was fishing for cats when his mother returned to him. Dorcas had made him a mouse with scraps of fur and tied it on a long string at the end of an old fishing pole. The kittens loved to chase it, and the boy liked nothing better than jerking it about the floor as they pounced after it. He seemed surprised when Cersei gathered him up in her arms and kissed him on his brow. "What's that for, Mother? Why are you crying?"
{Cersei X AFFC}

Map Guy's Translation:

Spoiler

Tommen was fishing for cats when his mother returned to him. Dorcas had made [Tommen into] a mouse with scraps of fur and tied it on a long string at the end of an old fishing pole. The [dragon] loved to chase [him], and the boy liked nothing better than [jerked] it about the floor as they pounced after [him]. He seemed surprised ("pouncing" is a surprised attack) when Cersei gathered him up in her arms and kissed him on his brow. "What's that for, Mother? Why are you crying?"

 

[GoldenGail3]

Death according to Maggie the Frog.

[Rose of Red Lake]

Dany expecting Tyrion to dispose of them would be fun.

[SeanF]

The Sand Snakes will probably get them.  Or Jon Connington.

[Endymion I Targaryen]

Quote

Obara would make Oldtown our father's funeral pyre, but I am not so greedy. Four lives will suffice for me. Lord Tywin's golden twins, as payment for Elia's children. The old lion, for Elia herself. And last of all the little king, for my father.

This Nymeria words are a foreshadowing of Tommen's fate. The breaking point for her will be when she realises or at least suspects who is Robert Strong. 

Myrcella was briefly crowned in Dorne so that counts for the prophecy. If someone is to become queen in the West, that's Cersei, not Myrcella. Westerlands are hers by birthright. Her daughter is needed only for a claim in Stormlands/Iron Throne. As for Myrcella I have two possible scenarios:

1. The Sand Snakes have arranged for her to have the fate that Cersei had arranged for Trystane (assasination on the way to King's Landing by brigants)

2. She is killed by Jon Connighton when fAegon takes KL

[rotting sea cow]

Myrcella is travelling back to KL. This is one way she could die.

 

[Megorova]

I think that Tommen will be killed by Sand Snakes, Nymeria and Tyene. They will do similar thing to what was previously done by Blood and Cheese. They will make Cersei chose which of her children will be killed by them and which will be spared. Cersei will chose to let Myrcella die, but they will kill Tommen, and when they will be escaping, they will take his head, same as Blood and Cheese took with them prince Jaehaerys' head. Queen Helaena chose her son Maelor to be killed and Jaehaerys to be spared, Blood and Cheese did the opposite and killed Jaehaerys, though Maelor later also died. He was torn apart by the mob, and his head was sent to King's Landing to Queen Rhaenyra. On the day of Myrcella's departure from King's Landing there happened a riot, during which High Septon was torn apart by the mob. This could be a foreshadowing to what will happen to Myrcella - she will repeat the fate of Prince Maelor and the High Septon, and after her death her head will be send to Cersei.