As far as I can tell there are no hints yet as to when Blizzard will next update Starcraft2.com. We probably haven't seen much of Zerg yet other than the Worms, Zerglings, and Mutalisk because Blizzard is still designing them!

If I were to guess, I'd say that Terran would be the next race updated on their site, if we don't see more units and buildings for Protoss first.