Originally Posted by Mr. Dent
None of that is going to happen though. Quicksilver is going to be used in one action sequence in DOFP. It will basically be a glorified cameo.
And in any case, as I have said repeatedly, Fox cannot actually tell the twins' origin, only Marvel can. Fox does not own the righrs necessary to tell their origin. The twins' origin does not involve Magneto at all. The studio that would have to alter the twins' origins is Fox, not Marvel.
Still, I don't see any problems with having Pietro in two movies, as narrative-wise his appearances are literally ages apart. If it's a cameo, what can he possibly do to contradict what Joss is planning for him? And DOFP will show the general audience he's a mutant, so while this can't be mentioned in TA2, people will still understand who he is.