Depending on what you mean, that is a feature of the new release: archon mode, where two players have shared control of a single base. This was also a feature of starcraft one but was never very popular. This time it should be easier to use and find matches through matchmaking. The recent blizzcon had a match between 4 pros in this mode, and the casters really couldn't keep up with the side engagements that were happening. So it's even interesting from a competitive scene as well.