Matt Grandstaff, Bethesda Softworks' Community Manager, has confirmed to Skyrim Nexus that intrepid game journalists will see Dawnguard in action at E3.
He was not able to release information about whether the content would be demonstrated or whether it would be playable. "Sorry, we haven't announced exact E3 plans. All I can say is that folks will be seeing it there," Grandstaff said.
Grandstaff confirmed that members of the general community will not be able to see it. "Something to keep in mind, most of our stuff at E3 is behind closed doors and appointment only," he said.