According to this CVG story, Valve's Doug Lombardi said at Games Convention this week that there's still a "50-50" chance of a PS3 version of Left 4 Dead coming out. Don't expect to see it any time soon, whatever happens.
"There's zero chance of it happening this year," he said. "It's something that's being talked about right now as the game is gaining popularity and looking like it's going to be a hit."
More through the link.