And Dave, you're totally missing the point of having a 10-yr old mutant - she's in the wings for when Logan dies next Wolverine movie. Must keep the franchise going, despite the aging stars...
Both Hugh Jackman and Patrick Stewart have said this is their last X-Men related movie, and given the events of it, that seems to be the case.
I suppose they could appear in flashbacks or alternate time lines or some such, and given the digital thaumaturgy Disney pulled with Peter Cushing in Rogue One
, I wouldn't put it past the studio to keep using their likenesses.
Who really knows -- there wasn't a post-credits teaser, so maybe they'll give the X-Men a rest for a few years and reboot the entire franchise.
There was a pretty clever Deadpool scene right at the start of the movie: Wade Wilson sees a guy being mugged, hops into a phone booth to change into the Deadpool costume (compete with John Williams' Superman music) -- and takes too long to change. They'll probably make a few more Deadpool movies just to keep the rights to X-Men from reverting to Marvel.