When Crecente shared tea and biscuits with Warhawk producer Dylan Jobe at GDC, he was told they were hoping to get the game's second expansion out by either the second half of March or the first half of April. Looking like it's the latter, as SCEA's John Hight told Gamasutra yesterday:
We just released an expansion on Warhawk in September, and we'll release another one in April.
April it is, then!
The State of PlayStation Network: John Hight Interviewed [Gamasutra]