Hot off the press from L4D411: Valve press release detailing an update that will drop in the Spring. It is reported to contain the SDK, Dead Air and Death Toll as versus maps along with a new mode called ‘Survival’.

I’m hoping for defence style gameplay with the Survivors holding out against waves of zombies and player controlled Special Infected. Maybe we’ll even get some sort of barricading mechanic. That would be pretty awesome in my opinion.