As long as Surefire's incandescent models sell, I'm pretty sure they'll be sticking around for quite a while. Arent the 6P and G2 still among Surefire's best sellers? I'd assume so, as they're the lowest price models and still afford a fantastic amount of output, not to mention modular components for versatility.
Edit:
Besides, none of Surefire's LED offerings quite replace their incandescent offerings. All the incandescent lights have a fairly tight hotspot and a decent amount of flood, whereas their current LED offerings are either all throw or all flood, with the notable exception of the K2 Kroma which seems to be, IMHO, of a happy medium.