People are seriously fooling themselves if they Think Apocalypse will be last X-men film and then Fox will focus on characters unknown to GA Instead of recasting.
For FC trilogy ignoring he emma Frost and Moira mactagget issues they
already recast Xavier,Magneto,Mystique,Beast,Toad,William Stryker,and soon will continue with Cyclops,Jean Grey,Storm,and Possibly Nightcrawler.
They will recast Gambit for eather apocalypse or solo film.
The entire purpose of time travel "Reboot" In DOFP was to continue making
X-Men films.
Fox will try to keep Hugh jackman as wolverine as long as possible but the idea he could never be replaced or fox would just dump the most popular X-Men character Is crazy.
I firmly expect Deadpool to take place In early 1980's so it can tie In with Apocalypse and possibly new wolverine solo film.Fox,Sony,and WB all want to follow the shared universe road that MS Is doing.