Remember Robert Downey Jr getting injured on the set of Iron Man 3? There kind of is an age limit.
And like as if that stopped him to sign up for Avengers 2/Avengers 3. And all people of all ages get injured on the set all the time.
At this point, recasting Cyke/Storm/jean wouldn't do the series any favors. And if its another prequel, its nothing really new.