i believe that the road triple will live on, mostly due to the preferences of elderly/rotund riders who want to ride the road on a mean-looking road bike, but do not have the chops for it at present. This is excellent news for folks who live in alpine areas like chris W described above; having a triple in a place like that might be nice for a performance-minded rider, who can enjoy both low gears and small steps between gears. The rest of us are better served by a double; in some cases, a compact double is the best option. (personally, i dig a 50/39. the 34t on most compact doubles is too low for south jersey, but the 53 found on most standard doubles is too high for my fitness level/laziness.)
Ppl who cherish their triples, but love 1:1 rear shifting actuation and the very nice doubletap road shifters, can just build their ride up with a shimano triple-compat FD and whatever triple crank they like, be it a shimano, and fsa, or whatever. Ppl who get all weird about the dearth of high-end road triples are typically living in a fantasy world; unless you're actually a competitive road-racin' cyclist, you can "make do" with the 10speed campy "triple comp" or ultegra.
As for the mtb world, i think the switch to 2x10 and the like will probably take a wee bit longer. I run triples on my geared mountain bikes, but i honestly use the granny ring VERY rarely. I'm also in south jersey, so why would i use the granny? Our trails're flat. But, when i rode mt allamuchy, i lived in my granny gear almost the whole way up that massive hill... As a recreation hefty guy, I probably could've made do with a 40/26 double and a 11/36 cassette or whatever they're using, but i'm not certain that racers'd appreciate that much space between the steps, gearing-wise.
just my $.02