"I dont know, I dont think they would take a game that is so close to L4D..."

first of all, it's not that close to l4d. left 4 dead is focused on co-op thing.
second there is game called "Killing Floor" which was a ut2k4 mod, then released as a game, and also a co-op zombie survival game.(even there is a fat exploding zombie with a poisonus bile, but that zombie was in the mod before the l4d )

so, i dont think there is a problem to get there. It only needs good advertising.