long-term - quakecon 2011 announcement, e3 2012 debut, ride the hype train through quakecon, gamescom, gamecon etc. with an october 2012 release.
short-term - early 2011 announcement, e3 2011 debut, quakecon hype train, october 2011 release.
Bethesda prefers to unveil a game at the same time as announcing it, when they do announce a game early it's because there is an agreement with another company which has to be announced (as in the case of Fallout 3 and New Vegas). Morrowind's expansions, Oblivion, and Shivering Isles were all unveiled along with their announcement and I'd expect the same for Bethesda's next project. As such I don't see an announcement at one event and a "debut" at another.
QuakeCon is more or less their own personal convention, though. they've never announced at E3 because it would inevitably be lost in the mire of all the other stuff that comes out of that; there's no risk of that at all at QuakeCon.
I think it's extremely unlikely that they'd unveil their own project at QuakeCon 2011 since Doom 4 is almost certainly going to debut at that event. Unveiling TES V or some other game at the same time would draw attention away from Id's projects. Even if Doom 4 debuts before then I imagine the QuakeCon spotlight will be firmly directed on it and RAGE.
This isn't to say we couldn't see a Bethesda game unveiled at QuakeCon, I think that's certainly a possibility in the future, but I don't see them doing this if id wants to do the same.
with history as a guide, do you really think they can actually churn out a game in three years? do you WANT them to churn out a game in three years?
About 9-12 months before Oblivion was released Bethesda Game Studios about doubled in size. This allowed them to get Fallout 3 mostly through pre-production while also finishing up Oblivion. Bethesda also has the ability to put everyone (or most everyone) on to one project if they want, something Fallout 3 no doubt benefited from for a short period and this upcoming game has gotten for much longer.