I wanted to take a risk and voted for Ellen Page. with the postive mind that Kitty IS on the script and Bryan wants to get Ellen back, even if she isnt the time traveler.
So if they get her back, maybe Bryan will want to announce her next. Since many sites keep naming Kitty and speculating if she will be back or not.
Halle and Anna are strong possibilities, for different reasons, but I go with Ellen this time
Lets see what happens in a few weeks
Next Big X-Men Crossover
* 2017- X-Men: Age of Apocalypse
Edit: Forget about 2017:
Official announcement -> X-MEN: APOCALYPSE - MAY 27, 2016!!!!