Well not really.
We've already seen confirmation that Whedon plans on using Quicksilver along with his sister the Scarlet Witch in Avengers 2. Well it looks like Quicksilver will be appearing in two movies.
Bryan Singer tweeted this today:
"Before he was an #Avenger, he was just a REALLY fast kid. Thrilled to say #EvanPeters is joining #XMen #DaysOfFuturePast as #Quicksilver."
Now when I read this I immediately jumped to the conclusion that maybe Fox and Marvel/Disney had come to some sort of agreement and that what we would be seeing is a younger Pietro in X-men and an older Pietro in Avengers 2. But it seems that neither studio has come to any sort of an agreement and it turns out that they're desperately trying to outdo each other and that if either studio could get the other to not use the character then they would. Rumors say that Quicksilver will have a small role/cameo but be a big plot point in X-men but Whedon plans on using the character and building him up in Avengers.