I honestly really hope not. If they want to give rewards for completing story lines and big achievements, I hope they do it in a more natural way than they did with NV. I don't want to suddenly be granted +5 damage with blades because I've dealt 10,000 damage with blade weapons all the sudden. And I really hope there won't be a little tracker on the HUD, letting me know how far along I am to some arbitrary goal. TES has always been about story and world immersion, and I feel like achievements have a detrimental effect on that.
Ehh... wrong achievements. We're talking gamerscore here.