Lol no! I don't know how many times i have explained that, but another faction with less units and buildings makes no fun and would be totally unbalanced, especially the Ori. It is simply too much effort to create the whole set of units and buildings for one more faction.
yes i know that, aswell they havn't got many known units that you can create... But what about making replicators playable, they got enough units, just add some buildings to create everything in ^^ (yea know, probably bad idea)
Yes, in space, but actually they'd need a lot of new ground units and buildings aside the satellites they'd need.
Furthermore, the 3 playable races will be perfectly balanced (hopefully^^), and a fourth would only ruin it.
And to repeat the reasons from the post above, it makes no sense to make them playable with only 2 ground units and 1 building, they need the same variety as the other 3 races, and this is, again, too much effort!