Well, due to the TWOW chapter previews, we know some things are going to happen: Arianne will go to the Stormlands to meet “Aegon” and the Golden Company, to assess them and see if Dorne should give its support to them. I think she will follow through on that — her TWOW chapters describe her as being skeptical, but once she meets him I think she will fall for his charisma and decisiveness.
After that, I’m not sure what will happen. Arianne’s conflicted feelings about Quentyn and Dany may make her consider uniting with Aegon on a more… personal level. (She certainly has a better chance with him than with JonCon.) However, the stuff in Arianne II about Elia Sand has me more than a little worried, especially the possible ominous foreshadowing. It could be that Arianne may attempt to get close to Aegon, but Elia will mess up those plans somehow. But either way I see her playing a role in the new conquest, and she may even become a queen, standing beside the mummer’s dragon as he is feted by the cheering crowd. (And note if this does happen I can see Cersei freaking out about Arianne, very very much.)
However, because I am certain Aegon is incredibly doomed, I am terribly worried he will take Arianne (and/or Elia) down with him. Possibly it’s JonCon’s greyscale that will get her, possibly it will be dragonfire. Though maybe she might survive — she’s not on my “definitely going to die” list, but I don’t have a lot of hope right now. Let’s see if she makes it through TWOW, and then I can reassess Arianne’s chances for endgame.