I thought it would be nice for something official. Bethesda is obviously going to be at the 2011 E3 event. As confirmed by IGN. No surprise really but still, its official.
http://wii.ign.com/articles/114/1143262p1.html

I think we will get a trailer at E3.

I think we'll get more than that. They might have those walkthrough videos like they had with oblivion so we should get a lot of gameplay footage too.

I really hope and think that we will be getting the gameplay walktrough's by Todd Howard. Those are always entertaining.

I'm sure they will have something similar to the E3 Oblivion videos, as in demonstrating the new AI and Combat and just the new engine in general.

well they have such a short time to release info and such so I would assume that at E3 they would do some gameplay videos

Hope they show gameplay of a quest or something

Trailer at GDC. Gameplay tutorial at E3 (as was done with Oblivion and Fallout 3). Lots of print media and online "previews" in September. Pre and Post Release TV ads on select channels. Rinse and repeat for Fallout 4.