I think the X-Men franchise has far more potential than they seem to give it credit. So many characters, so many story arcs, so many potential ways that themes can be dealt with. Look at Unbreakable for example, a classic representation of the Xavier-Magneto relationship, even the more recent Heroes TV series is in essence a representation of what potential X-Men has, but the studios seem to think it all depends on Wolverine.

From Hollywood Reporter through Coming Soon we have the following:

The studio has been so eager to get "Wolverine" out next year that it has committed to go into production the instant Jackman finishes Baz Luhrmann's epic romance "Australia," which Fox is tentatively set to release next year...
For the time being anyway, it seems that "Wolverine" is the best hope for continuing the "X-Men" movie franchise. "There is no script for an 'X-Men 4,' and there is none in the works," avers producer Lauren Shuler Donner.

Don't get me wrong, Wolverine is a brilliant character, the mystery around him, the intense mental scarring, it gives him a personality that works extremely well on-screen, I can imagine it also allows a fair dose of creative freedom for the writers doing stories for him, knowing that there is a huge gap in his past to play with, but is he really so great that the franchise depends on him and him alone?

Written by Ramchandra, edited by Louise