If it is TES:V, I doubt they'll be announcing at any major gaming convention.
Normally, they put a screenshot and/or interview in a magazine, while updating their site at the same time. As word spreads, they release concept art, further screens, and the like.
In all fairness to your statement above, Bethesda just picked up the IP of fallout 3 and released the game last year (right?)....as of now its set out to be far more successful than Oblivion, especially amongst the casual audience. How did they first debut it?
Perhaps they're trying to use the same tactic they did with fallout when it comes to marketing the next elderscrolls title.
Call me out if im crazy, im just trying to spread the hope-jam around.