We're not going to call it an actual expansion until they do, but it sounds like there's a serious amount of new content in the works for Vanguard: Saga of Heroes. The game's lead designer Salim "Silius" Grant was recently interviewed at Allakhazam, and he spilled the beans about what to expect in the way of patches over the next few months. We're talking two new dungeons with both group and raid components (which were previewed at SOE's Fan Faire '08), an Alternate Advancement system that might sound familiar to fans of EQ1/2, item enhancement, and an increase to the level cap.
Whether or not SOE decides to tie all of this new stuff together as an expansion of sorts is of little consequence, because -- and here's the best part -- it is all intended to be free. For a few specifics: currently, the level cap will raise to 55, and this does mean that classes will be getting a mix of both new abilities, and upgrades to older ones. The AA system will be modeled after the one found in the original EverQuest, and there will be passive bonuses like stat and run-speed increases, as well as class-specific bonuses.
As for the dungeons, one will help players to get from level 50 to 55, and the other will be for 55's and will feature some AAs. To get the full scoop on these things and more, make sure to check out the rest of the interview with Silius.