In a Variety article talking about investors it is mentioned that Legendary is on board for the Superman Returns sequel:
If Legendary is unnerved, it isn’t showing. Like Warners, Legendary insists it will turn a profit on “Superman Returns,” and has given all indications that it’s on deck to co-finance a sequel.
Like Legendary, all the funds argue that they won’t be made, or broken, by just one pic. By investing in a slate of pics over the course of several years, they’re virtually guaranteed a return of 10%.