Ok, so this is my first post as a contributor and I'm glad to do it. This is a long-shot post and it's all based on a theory which is: Spiderman will be a member of the X-Men. You wanna know why I think this? Here's why...
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First off, Marvel is great at making big announcements out of little things. For example Robert Downey Jr. showing up in a post-credit scene for The Incredible Hulk movie. This silent move, showed a lot of us that A. Robert Downey Jr. will be a Marvel character and B. There will be more Marvel movies on the way. The post credit scenes have given Marvel power of there audience to keep them in the theater a little longer, and also gave them something to think about for the trip back home and longer, so when I saw the post credit scene for [The Amazing Spider-Man 2](movie:508593), it made me think long and hard about it.
Anyways keeping this in mind I start to connect the dots. Marvel already had a couple of post credit scenes in line for the movie, but they decide to use a scene that has nothing to do with the actual movie, but with an upcoming movie. Why is that? Because Marvel is trying to pull one over us, but not this time. Also, Peter Parker in the comics have been denied from being in the Justice League and an Avenger. It was only a matter of time before he tries to be a member of the X-Men. Of course this will probably happen in the comics before it shows up in the movies, but it will be a year or to since the X-men is coming soon and there's no way he's already in it.
So there you have it, my reasons to believe that Spiderman will be in an X-Men movie, and or possibly be a member himself.
Please write in the comments what you thought was wrong with my theory/post: all thoughts help!!