Offering alternate way of the presumed burning. It's pretty obvious to a lot of the fandom that KL will be burned. I don't think it will go down the same way as in the show (crazy woman on a dragon) even if D & D had a template b/c many characters were missing. I think GRRM may opt for a classic Westeros politik move to accomplish this instead. I think that Aegon's reign will be met with cheer, but looking at the situation in Westeros: Winter famine, the others, Stannis' rebellion, redistribution of land to his foreign allies (gold company); gray scale outbreak , Euron raiding and rebelling, faith of the seven now being an armed - cheers will not last. So I think instead of mad Danny getting on a dragon and burning the city, I think what makes more sense if for her an Tyrion to intentionally drive Aegon to make a bad mistake banking on his desperation to kick him out of the Cyvasse board:
- Daenerys has proved her cunning tricking the masters in Astapor, she also got her people to successfully take Meereen. She pulled a trick more than once she can do it again. Her character is going through a change, but that doesn't mean that she'll come back overtly violent. I think that it will be more interesting for her to come back as more of a Visenya type - less emotional, more pragmatical, threating and more keen to using violence as a means to an end at a precise moment not for violence sake.
- With Tyrion at her back and all the stuff she's learning in Slaver's bay she can definitely come up with the types of political tricks that could easily match a red wedding. So she doesn't have to burn kings landing herself but Tyrion and her can easily drive a desperate, inexperienced stressed out king to make a big mistake that will get him killed.
- It doesn't make sense for Daenerys come back overtly "fire and blood" when she needs Westeros on her side. I think it's most likely that she will rule with influence at first until people realize who the real power in Westeros is. All she has to do is arrive in Dragonstone and park her dragons and army by DOS when things are really desperate and just watch Aegon come asking favors ("Auntie can I have a dragon, auntie can I have an army, auntie this auntie that" even if Tyrion told him not to do this). Asking will give Danny a chance to publicly step in to fix Aegon's problems until soon enough the lords of Westeros understand who really rules House Targaryen and start considering Aegon as weak.
- I think that Daenerys frustrate Aegon by reserving the right of giving him a dragon and challenge him to prove himself worthy of being a king w/o needing her so much. It is likely that Aegon will grow infuriated that his own allies will lose trust in him and in order to prove himself he'll try to steal a dragon and not knowing how to control one (or not having dragon's blood) he will burn kings landing and go down in flames with the city.
- For Daenerys mission accomplished - she tricked her nephew, got him out of the way and power resides where people think it resides. She becomes the queen of the ashes with support and so what's left is the war with the others where she'll meet her end. I think that she will become overly confident and cruel and get stabbed by Jon Snow, but it will be because she'll make a dumb mistake and get herself turned in a white walker so powerful that can can control dragons and Jon will have to stab her in the heart with a dragon glass knife or long claw.