According to "a trusted source", IGN is reporting that Insomniac Games - creators of both Resistance and Ratchet & Clank - is about to abandon the land of PS3 exclusivity and become a multiplatform developer.
Despite long ties to the PlayStation brand, Sony doesn't own the studio, so if the team decided to go and make games for the Xbox 360 (or the PC or Wii), there'd be nothing stopping them.
With both the developer's flagship properties, Resistance and Ratchet & Clank being Sony-published titles, don't expect to see them appear on a different system. But Insomniac's next project? If this turns out to be true, it could be developed for as many platforms as the studio's heart desires.