About the title, if they don't want to use "Age of Apocalypse" because transformers and Avengers are already using the "Age of " for their films.
How about "X-Men: The Apocalypse"? Its simple yet striking.
X-MEN: DAYS OF FUTURE PAST
The future of X-Men's original trilogy cast begins this May!
Hugh Jackman - Halle Berry - Ian McKellen - Patrick Stewart
Anna Paquin - Shawn Ashmore - Daniel Cudmore - Ellen Page