So I stand corrected. Heart of the Swarm introduces 2.5 new units for 2 sides (mines that don't look particularly effective and a proto-mothership with a few abiliites being the halves), and 2 units for the zerg. Wooo.
2.5 years for that. Amazing.
And I'm not sure what some of the units like the warhound are supposed to be, but others look fairly underwhelming.