I don't either.
But they could, really easily, for the 4th.
Just show him responsbile for the "cure" (the motive would just be he knew that Magneto and others would take action so he was wanting to start one of his Survival of the Fittest Wars), and have Mr. Sinister revive both Cyclops and Jean. Meanwhile, because the mutant "threat" is growing again, have the Government launch out Sentinels to capture mutants.
I mean, there's so much crap to do. Fans can come up with stories way better than these directors sometimes.