When I look at all the things that need to happen in The Winds of Winter for Daenerys to even end up in Westeros, I am not sure that George RR Martin has the storytelling discipline to make it happen during that book.
Spoilers Ahead (I guess)
From a POV perspective Daenerys only had 10 chapters in A Dance with Dragons. There are other POV characters that are going to be involved in this as well, Tyrion, Vicatarion, random BFS chapters if GRRM chooses. There is just so much story to try and tell.
So in the last Daenerys A Dance with Dragons chapter, Daenerys ends up surrounded by Khal Jhaqo’s khalasar. Jhaqo famously abandoned Dany’s husband Drogo as he was dying. In the process stole Daenerys khalasar away from her. So we can pretty much assume that Daenerys is going to get revenge on Jhaqo and a few other Dotraki in the party. Then Daenerys is going to take control back of her khalasar, with Drogon either in tow or nearby.
I am assuming this is going to take at least a chapter or 2, just for this plot point based off of Martin’s writing style.
From there Daenerys most likely is going to head back to Mereen, again, I don’t expect this to be a short adventure in the book.
After that Daenerys gets back to Mereen either pre or post battle that is getting ready to start. I likely think she is going to be involved in the battle, so that’s at least a chapter for the battle, probably a pre and post battle chapter.
She also needs to wrangle up Viserion and Rhaegal - another chapter.
The Harpy will probably get some time as well.
Victarion Greyjoy is also going to be request her attention during this time, and I bet we get to see if Dragonbinder works or not. - Another 2 to 3 chapters.
Then she has to integrate her khalasar, likely Ironborn, Freedmen, unsullied, and all her sell swords together and somehow rule Mereen, at least for a little bit.
Undoubtedly Tyrion is going to meet her in a plot point that will take up some time.
All the while trying to arrange a large enough fleet to take all of these people which at that point is what 30 to 40 thousand people?
I also have a hard time believing that even if she leaves Mereen in this book that there isn’t going to be a stop/look at Valaryia and Dragonstone.
As I look at it, there is just too many plot points dangling out there currently, without any new ones being introduced for Daenerys Stormborn to end up in Westeros by the end of the Winds of Winter.