Originally Posted by Alexei Belyakov
There's no logical justification for bringing back Marsden & Janssen.
It would feel cheap & nonsensical, like Marvel bringing back Coulson for The SHIELD series.
Xavier & Rogue may not have been in the future faction of DOFP, but if Singer puts them in it could at least make sense. Same goes for Mystique.
Jean & Scott as children if Singer bumps up the FC faction to 1980 I could accept.
We don't know how much time is between X3 and DoFP future, it could be 10–20 years? Even a few months after X3, Jean could have resurrected, she's Phoenix. And Cyclops could have been found to be alive. We never saw him explode or disintegrate like the others, this doesn't go against what happened in X3 either.