I wonder what the deal is with U3 engine games if the actual game slips (like HL2 and D3).
Like Vampire, it probably wouldn't matter much. They aren't waiting for the game to ship, if anything they're just waiting for Epic to deliver any critical patches or features ... and there might not be a lot of those. Epic has been pretty smart about layering their technology on so that licensees can take advantage of features as quickly as possible, as opposed to Valve and iD who seem to only license completely builds.
More than the engine though, Epic is very developer friendly. A lot of the stuff they've added with UE3 has more to do with production pipelines than rendering tricks it seems.