Re: Bryan Singer Directing X-Men: Days of Future Past - Part 2
"In March 2011, Shuler Donner revealed that the film was in "active development at Fox," saying, "We took the treatment to Fox and they love it... And X4 leads into X5""
X-men (film series) Wikipedia
Now I'm almost certain that Fox has revised the possibility of X4 or X5... I think Days of Future Past is that revision. However, just because they haven't given a green light to something doesn't mean that their aren't scripts already written for X4... Studios have many scripts laying around written by various people... doesn't mean they will use them, and if they do use them they will have someone take it and rewrite it. There is no reason to think that X4 isn't in active development. But yes, they will wait to see how The Wolverine and DOFP work out before they continue.