So, it seems likely that at some point Team Aegon will make a move on King's Landing and try to take the capital while Cersei is still inside. There has been lots of discussion whether it will happen before or after Cersei's fight with the Tyrells, whether wildfire will be used, and whether Daenerys will be involved, but I think there is one vital detail we have been missing.
Last year, I went to a talk with GRRM which was partly about the influence of medieval history on ASOIAF and he was asked a question about if there were any particular medieval women that influenced his female characters. GRRM mentioned Eleanor of Aquitaine, before moving onto this interesting anecdote (you can hear the original recording here
, with the relevant bit starting at 46:20. I have also transcribed it below):
GRRM: There is also a lot of... um... if you read the Italian histories... a lot of the... uhh... during the Italian Middle Ages and Renaissance there were a lot of very powerful and bloody women who controlled various city states in Italy and did some amazing things. There is one very famous story that is once again probably made up by some popular historian or legend maker, because it occurs in like... the same story is told of six different men and at least two different women and it's one where they... the father and or mother, is in a castle and they have a son outside who they're going to hang. Surrender the castle or we are going to hang your son right in front of you, and this story is told of William Marshall, the great knight's father, who supposedly pulled up his jerkin or whatever the hell he was wearing and showed them his dick and said "go ahead hang him, I have the equipment to make more". And that same story is also told of, I think, of Caterina Sforza, the Italian. They were going to hang her son and she lifted up her skirts and pointed at her vagina and said "no, I can make another one, see right here". So probably it never happened at all since it is attached to six people, but god, it's a great story. I can't resist things like that and then don't be surprised if I steal it and you see it in a later Game of Thrones book.
At the time, I thought it was just a throwaway comment about how he is inspired by history (earlier in the talk he had discussed the Black DinneRed Wedding parallels, the Wars of the Roses, and Hadrian's Wall), but the more I have thought about it, the more it seems that something like this could feasibly happen in the timeframe of TWOW. For this scenario to happen we need three things in place:
- A woman being besieged in a castle (although GRRM mentioned that this siege story was also applied to male figures, he brought it up in response to a question about influential female figures, so I really think he intends for this story to be applied to a woman).
- The woman has a child who is being held by the enemy.
- The enemy is willing to sacrifice children.
It seems quite clear to me that in Cersei, Myrcella, and JonCon we have those three points covered.
Firstly, it is a bit of a fandom consensus that Cersei will survive her trial and regain some sort of power in King's Landing through her son Tommen. By killing Kevan, Varys made Cersei the last Lannister standing in King's Landing and it seems that, once she survives her trial, she will build her power base again. However, given that the Golden Company has invaded the Stormlands, it seems likely that the Crown's control over the lands around King's Landing will shrink and the Crown's last base may be the capital. Given that Kevan is dead, Jaime is missing, and Cersei will have alienated the Tyrell's, it is likely that she will be the one in charge of the defence of the city when Aegon arrives at the city's gates. If Aegon is the valonqar, this turn of events would be interesting, as a siege could be construed as a "choking". You might ask why Cersei would be so blasé about Myrcella's life given the prophecy, but I think it is possible that if she defeats the Tyrells/Margaery, she will believe that in defeating the YMB she has defeated the prophecy, therefore being more reckless with her children's lives. Cersei flashing the besieging army may also fit with her slow descent into paranoia and "madness" that we saw across AFFC and ADWD, so it may be in character for her as opposed to other women who are holding various castles.
Secondly, Team Aegon have an ace up their sleeve. Myrcella is currently on her way back to King's Landing with Nymeria and Tyene Sand. Nymeria has been sent to take up the Dornish seat on the Small Council, while Tyene has been sent to liaise with the High Sparrow. Both sisters still burn with the desire for vengeance against the Lannisters for the death of their father. Simultaneously, we have Arianne and Elia Sand heading to Storm's End to check out Aegon, and a popular theory is that there will be some sort of alliance between Aegon and Dorne that will facilitate the Dornish switching sides. Given that Myrcella is currently in the hands of Nymeria and Tyene, two of the characters that most want vengeance against the Lannisters, it is possible that they would consider handing Myrcella over to Team Aegon after an Aegon/Arianne marriage to demonstrate the Dornish goodwill. Doran might be unhappy with that plan, but he is currently too far away in Dorne to do anything about it. Team Aegon would rightfully see Myrcella as a threat to Aegon, and would likely want her under their control, which would explain why handing over Myrcella constituted part of the marriage agreement. Alternatively, Team Aegon could waylay Nymeria, Tyene, and Myrcella on their way to King's Landing, and effectively kidnap the young princess.
Finally, Team Aegon has a military leader who would be willing to sacrifice children in order to make Aegon king the form of Jon Connington. JonCon feels deeply guilty about failing Rhaegar at the Battle of the Bells, and would likely force himself to be ruthless in order to protect his (supposed) son. Myrcella's potential death would also be a direct replay of Rhaenys', allowing some thematic resonance in JonCon's acts. There are also lots of theories about JonCon doing something crazy at the siege of King's Landing due to the "bells" reference in the show, and this could just be one part of JonCon's more ruthless behaviour at the siege. Threatening to hang Myrcella could be another.
What happens after this point, and whether JonCon actually does kill Myrcella, is up for grabs, but I think it is a definite possibility as to something that could happen in TWOW given the shadow of Rhaenys' death. tl;dr
Given what GRRM told us in his 2019 Waterstones interview, it seems that at the Siege of King's Landing, JonCon will threaten to hang Myrcella (who had been given to him by the Dornish) unless Cersei surrenders the city. Cersei, who will have descended into madness by this point, will flash the people besieging King's Landing and tell them she has the equipment to make more children.