I'm not sure that a reboot would be a wise idea. Terminator: The Sarah Connor Chronicles showed that the franchise had artistic legs without James Cameron, but a movie reboot would probably entail a back-to-basics retelling of the original story. The original story, though, was basically Cameron's alleged fever dream on celluloid. I don't see a manufactured and commerce-minded retread faring well against such a seminal and driven movie, unless perhaps Cameron himself decides to take up the reins. That's not likely to happen in the next five years, if ever.