when I name AoA Im not talking exactly about the same storyline, but to do a big movie crossover with Apocalypse as the ultimate villain, the horsemen, Archangel and all of that.
Id do a mix of storylines too, but keeping Archangel, and using both Sinister and Apocalypse.
A Two part would be perfect, shoted back to back and to be released in 2017 and 2018. This way the OT cast could film just in 2016, and Fox could use this crossover as their big final goodbye.
What I dont find smart by Fox is to pretend they could use OT cast again in 2020. To shot back to back is the best option in this case.
Next Big X-Men Crossover
* 2017- X-Men: Age of Apocalypse
Edit: Forget about 2017:
Official announcement -> X-MEN: APOCALYPSE - MAY 27, 2016!!!!