IIRC aren't animal people eventually planned to have (non-civ level) tribes along with settlements and so on that you could visit? Perhaps they could raid as well so the "early invader" idea is probably already in Toady's head (though it might take until the "hill dwarf" arc for that to happen) - goblins still fill the "raider faction" idea, though since they require no sustenance its moreso that they raid for fun rather than raiding out of neccessity. I imagine that with the procedural civilized races that both "raiding out of neccessity" races as well as "early invader" ones will be possible.
As was mentioned before, Toady doesn't want to merely recreate a standard fantasy setting, which is why orcs aren't a thing and most likely won't be as their niches are already filled by other things; he wants to have a simulation with detailed magic, economy and myth systems; one of the myth goals (atleast, IIRC it was slated for that release) was having procedural civilized races as well, so as Shonai mentioned, its possible that in one of the worlds you generate you'll have a race that will have some kind of a different name, but will for all intents and purposes nail every "orc" stereotype.
I'm guessing that more site types will eventually be a thing as well (perhaps raw-modifiable as well, or made with some kind of editor), again for the mythgen stuff, since having the different procedural races having the same types of sites as now would be rather boring and wouldn't make much sense either - so there isn't much of a point to quickly introduce a new race to the main 4 (or 5 if you count kobolds) just to have a different site type.