No, it's 99.9% likely to NOT be an announcement about Full Throttle 2, as nice as it would be, but much much much MUCH more likely to be the widely rumored KOTOR MMO (aka the worst kept secret in the biz). Rumors of the existence of such a game began back last October when "a source close to BioWare" said that the MMO that BioWare was currently working on was going to take place in the KOTOR realm. That same source also said the game was targeted for a 2009 release, which would time up perfectly to this announcement.
Rumors of the game were further fueled this July when LucasArts filed trademarks for the names Star Wars: The Old Republic, Star Wars Legends, and Star Wars Sagas. Would it not make sense for the MMO to be called The Old Republic? While we may not know what exactly LucasArts and BioWare have cooking for us until the 21st, we do know that it does have something to do with Star Wars.
I'll keep you posted as to what happens!