It's planned for a standalone. It's estimated release is Fall 09 with a cost of 20$ and 40$ (Black Marine Armor and access to Alpha). If you preorder now you can participate in the Beta when it's available.
And it's true that the majority of the community moved to Combat. It's a pity though, because the real game was so worth learning in order to play. Their approach to NS2 now, however, is to find a legitimate balance between different classes. The onos, instead of becoming a running devouring machine is going from dps/tank to tank/support and a little bit dps. They took out devour and put in a bone shield (I'm thinking a half sphere) so they can wipe out stalemates at certain points in games.