X-Men Apocalypse: 10 Implications For The X-Men Franchise
9. The Dark Phoenix Saga Is Coming
Apocalypse made it pretty clear that young Jean Grey will be one of the principal players in the new X-Men franchise, evidenced no more than by her unleashing the Phoenix Force to destroy Apocalypse at the end of the movie.
It's particularly telling that, as the Force envelopes Apocalypse, he says, "All is revealed", which is surely a tease for future Phoenix shenanigans down the road.
The most logical plot would be the iconic Dark Phoenix Saga, which sees Jean Grey possessed by the Phoenix persona, transforming her into a villain who faces off against the other X-Men, before she commits suicide in order to destroy the Phoenix.
It's suggested earlier in the movie that something dark is growing inside Jean, both in terms of her nightmarish premonition and the fact that she burns the walls up in her sleep. As much as she can be a force for good, she's almost certainly going to become a temporary antagonist in at least one of the next three core X-Men movies.