According to fan notes, the expansion will be dubbed Delta Rising and will take place in the eponymous Delta Quadrant, introducing species such as the Talaxians, the Ocampa, the Kazon, and the Malon to the game's lineup. Captains will be able to hit level 60, with a new method of alternative advancement and a new set of Tier 6 ships to be unlocked and flown. New Voyager interiors and Intrepid models will be available, along with voiceovers by Tim Russ and Garret Wang (Lt. Commander Tuvok and Ensign Harry Kim, respectively). If it's all true, all we're waiting on are pictures -- and of course, news about the new ships.
[Thanks to Anon E. Moose for the tip!]
[Update: Tipster Anthony let us know that TrekMovie.com has more information and photographs from the event at which the expansion was announced.]