Yep. It's official.
Todd Howard confirms in Game Informer, that the new "Dragon Shout" system in Skyrim is going to amount to the use of Thu'um. It will be an in-game mechanic, unique to the player and the Greybeards, due to the influence of the gods.
This means a few things. First, it essentially means you're a new Tiber Septim. Of sorts.
Chosen one of destiny, named as the Dragonborn? Check.
Climbing to High Hrothgar to meet the Greybeards? Check.
Using words of various power in the same form the Dragons are supposed to? Check.
Summoning an actual Dragon in game as an ally? Yep, that's happening too!
Although, I must say that the idea that Thu'um originated as the Dragons' own form of magic, with Nords learning and co-opting it for their use, seems a bit more like Bethesda's reputation for going with a unique path on things. The Nords have a healthy respect and general level of fear with regards to Thu'um and dragons alike (their views on Alduin being a perfect example), so this idea seems like it has promise.
As always, though, November should reveal all.