This was revealed at a GamesCom 2012 interview, in which he stated, “There’s a set number of units that should be in the game, but we just don’t know 100% what that is.”
”Initially in Wings of Liberty we went with 13-14 units, which is similar to what Brood War had,” he explained, “When we started exploring a bit more we tried to stick to that rule, but when you’re taking units out and putting new stuff in, there are some problems. Wings of Liberty is pretty solid in terms of each unit being useful in a certain scenario – we tried saying, well what if 15 is the right number, or 16 is the right number?”
Overcomplication was a design issue that Kim states will not be tolerated.
“After trying it out, we think it’s okay to add a couple of more units, but at the same time we don’t want it to go too out of balance, so that it becomes too complex,” he noted, ”That’s something we have to watch for during the beta, and really make sure that the number we have right now is good for the game.”
No unit is safe from being removed, Kim promises. It all depends on the upcoming beta testing of Heart of the Swarm.
There is no set length for the beta, either. “As long as it takes us to get the game where we want it to be,” Kim insisted.