I also don't feel like book Dany would never concede the Throne. She has tunnel vision on it. I can easily see book Dany becoming the villain but it will make so much better sense than how show Dany's arc went. I think Dany would and likely will die before she will let go of her quest for the Throne.
Since W&B says that King Bran came from GRRM, I feel like Jon will name Bran his heir should he not return from fighting the Night King. I largely feel like he will die and end the Targaryen line with him but I could see him maybe staying beyond the Wall by choice at the end.
I'd love to see the Doom of Valyria too. The Targaryens weren't even a particularly large or important house in Valyria, one of the smaller dragonriding houses. So what did it look like in its prime? How big were their dragons? What happened?
We see how powerful the Targaryens and their dragons are in Westeros so just imagine a world where they were a minor family. 🤯