It would really depend; most real-time strategy games set in space rarely feature more then three races and turn-based strategy space-empire games on average feature more then eight races. We are on middle ground with this game being a Space-Empire RTS, but most of those to my memory featured more then six races (only exception to memory was Haegemonia).
We got to keep in mind the additional resources required to concept, design, develop, and balance out each additional race with a Space-Empire RTS in the year 2006 and beyond. This game is coming with more features then the typical Space RTS, so, let's keep that mind as well.
In addition, there is always the probability of an expansion, if and when the game becomes successful at retail to warrant it. Edit: That might include a new race or two.
On the topic, I would appreciate seeing more information about this game being released on some kind of consistency. For instance, a new screenshot every week, a new ship or structure every two-three weeks, and so on.