Here is some news about superman returns sequel from dark horizons:
"X2" and "Superman Returns" scribes Michael Dougherty and Dan Harris have opted not to come back and pen a sequel to last year's 'Superman' with Warners now taking pitches from other writers reports Variety.
The "Superman" film franchise's future is presently in a kind of limbo state thanks to the impending Hollywood production strike, Director Bryan Singer's busy schedule, the upcoming and much further along "Justice League" movie (which has Superman as a major character), and the lukewarm critical and box-office reaction to 'Returns'.
As a result there's industry talk that, much like the upcoming "The Incredible Hulk" with Ed Norton, the studio plans to start afresh - basically ignoring the last film to start a whole new continuity.
The studio however has denied such plans, saying the next would be a sequel with Brandon Routh returning. Either way Legendary Pictures will be back to co-develop and co-finance the project.
The delay means the project would certainly not go into production until 2009 at the earliest - making a Summer 2010 release seem the obvious choice to give the studio a revolving cycle of Summer superhero films (Batman 2 in 2008, Justice League in 2009, Superman 2 in 2010, Batman 3 in 2011, etc.)"