Anyone know if there are really only 3 races?

Maybe they hate every single race and try to destroy the three races so the races would probably team up?

 

If the Xel'Naga came back, with an army, wouldent they own all three races? I mean, they traveled space, made temples of mass destruction, and evolved speicies a few what... umpteen thousand years ago? Imagine what they could do now!... with their armies!...

Not sure bout the hybrids though...

 

No fourth race according to me, but special units, just in the campaign ! Xel'Naga and Hybrids in the storyline.