I have been feeling some pressure lately, thanks for asking.
Seriously, I think Singer making a sequel to SR will sink Superman as a film franchise for another two decades. I am a critic of his that cannot be silenced.
SR cannot be redeemed. There was no chemistry between the leads, Superman had very little screen time and dialogue, and the entire Super Son concept as put forth in this film is atrocious and irreparable.
I think the studio is facing the reality of this situation. If they let Singer make a sequel, it'll be on THEIR terms now more than ever, in light of TDK. Singer probably won't like that, as he probably wants to make another "woe is me, I'm an outcast victim and Superman should be too" film.
So the WB needs to let Singer go. The fans need to let Singer go. Superman Returns can stand as an epilogue to the Donnerverse, albeit not a very charming or entertaining one.
In about three or four years, someone else needs to start from scratch. That DOESN'T MEAN origin story, it just means getting a new aesthetic distinct from the Donnerverse.
I think the perfect guy to write it is DC Comics's biggest star writer, Geoff Johns. He was Donner's assistant and is a hell of a writer whose "Last Son" arc should have been Superman Returns. Had it been, it would've been a tremendous, rousing, epic TDK type success, and we'd be waiting for a third Superman film now, not hoping one will get made someday.
Johns's arc had Clark exploring fatherhood through adoption (perfect considering his own history), a building of Kryptonian history, and not only Zod and his pals, but an entire army of rogue criminal Kryptonians from The Phantom Zone.
My point is, there are other people out there who can A) do tons better than Singer did and B) deserve their shot.
Singer had his, wasted it, and should be made to move on if he's not willing to do so himself.