So one wonders what other time-and-space bending casting decisions might come next. Since Jennifer Lawrence (Raven/Mystique) has definitely signed on, could we also see Rebecca Romijn return to the role? Hank McCoy/The Beast was portrayed by Kelsey Grammar in X-Men: The Last Stand, so would he return to stand side-by-side with Nicholas Hoult?
And furthermore, will the future and past (see what I did there?) versions of the characters appear simultaneously, or exist only in flashbacks or flash-forwards? Will both older and younger Magneto and X have substantial screen time, or will they use McKellan and Stewart in a way similar to 2009's Star Trek employed its Leonard Nimoy cameo?