Yes Loskene, both the Tholians and the Gorn are in the game. They even have their own ships too!
As for your crazy expansion idea - that's also in as well. They don't do it at the moment simply because they haven't got colony ships yet (I'm still implementing them) and because the AI (Artificial Intelligence) hasn't been added yet. As you said, not all of the races can expand. About a third of them will expand aggressively, another third will be able to expand but will take a long time to do it, and the final third won't be able to do so at all.
The Borg are still in limbo, but they definitely won't be a playable race; the general concensus on the forums is that people want them to be an unplayable, ever-present menace that could strike at any time - so chances are they will be in as a random event. Incidentally, the random events haven't been implemented yet, but i've written a huge list of possible random events and race-specific event messages Here. This list has NOT been agreed on by Mike - he hasn't even said that whether he wants random events in the game, let alone what those random events will be. I just wrote that list to see what I could come up with, and I haven't finished it yet. Fingers crossed at least some of them make it in the game.
