I don't mean today's top end bikes, I mean bikes that aren't even on the drawing board. Ever just wonder what the world is going to bring in the next 10-20 years to our little hobby? I know we're about to see electronic shifting in the road bike world, I'd assume that'll make its way down to mountain bikes. I'm sure there will be teething problems, but in 20 years the cable will probably go bye-bye and we'll never have to tune another deraileur and every shift will click in quickly with precision (as the electronics will be able to manage a lot of the timing that today is left to chance).
How about suspension? Someday I think we'll see the magneto-rheological suspensions like Corvette and Ferrari use on some of their road cars. Suspensions that can vary the damping within miliseconds based on inputs from a computer. You could use a laptop to "tune" your suspension infinitely to fit any terrain. Heck, have the program automatically change with GPS input so you can tune your bike specifically for every inch of a trail. Or have it figure out the exact best damping from displacement and acceleration sensors.
Carbon-ceramic brakes like high end road cars use now? Possible. It would allow brakes to get much hotter and thus much smaller and lighter than what we have today.
Kinda fun to daydream about the future. Maybe some of this stuff is even available today, but the nice thing about the march of technology is that even the exotic stuff today will probably be commonplace in the future.