Originally Posted by Dark Raven
In the Hype's interview with Kevin Feige, he said that both Fox and Marvel were able to use the characters, but Marvel couldn't make reference to mutants or Magneto.
The last bit is significant about whichever one uses them first gets to keep them. Now that may not be necessarily legally, but in the public eye, that would be the version of them first established. So maybe it's a rush to get Scarlet Witch and Quicksilver onto the big screen first so that the Marvel version will be the true version and anything Fox puts out will be seen as a pale imitation.
Sharing characters with a billion-plus box office megahit is not a bad position to be in, pale imitation or not. I could see FOX incorporating their version of the Maximoff siblings into the DOFP follow-up as a way of drafting off of the success of the Avengers sequel.