A question that is always raised about the Marvel Cinematic Universe is when will the X-Men show up? The answer has always been whenever the lawyers say so.
Good news though! It seems as if that day is coming soon. Disney (who owns the film rights to the Avengers) and 21st Century Fox (who owns the film rights to X-Men and Fantastic Four) are discussing a merger and it looks like talks are nearly finished. If the deal goes through it is rumored that we will see the X-Men in Infinity War and certainly after that.
This is a very exciting time for superhero fans and already people have guesses as what this all means.