Let's consider what would "kill" EF mount. The only thing I can think of is EVIL, and even then that's a bit of a stretch. I'm not talking short term here, but suppose in the distant future we have an EVIL camera with AF system that is as good as DSLR phase AF in every way. That would be enough to obsolete crop sensor DSLRs, and only leave FF serving a niche position (unless Canon goes FF EVIL!), and who knows by then "affordable" medium format might be squeezing that space too.
The post above on video is interesting but I'm not familiar enough with it to guess any possible impact there. Videographers seem to be doing well enough with current kit. What lens functionality additions would increase value for video use? Consider what might be done in body as opposed to lens too.
Canon 1D, 300D IR, 450D full spectrum, 600D, 5D2, 7D, 7D2, EF 35/2, 85/1.8, 135/2+SF, 70-300L, 100-400L
EF-S 10-18, 15-85, MP-E 65, Zeiss 50/2 macro, Sigma 50A, 150 macro, 120-300/2.8 OS, Samyang 8mm fisheye