A Naughty Dog employee said that the next PS3 Firmware update will include cross game chat. Since then, I think the post has been deleted, but here is a copy of what he said. Sony of course doesn’t comment on rumors. So we’ll just have to wait and see.

Would you use cross-game chat? I myself probably wouldn’t or very sparingly.

Reported statement made by ReklissAbandon:

“I think they wanted people to have fun and ejoy the show since all dead players can talk to each other no matter what team you are on. But I will suggest it anyway. Not to mention that the next PS3 firmware update is going to allow cross game chat. So if players use that instead of in game communication then they would also be able to communicate enemies positions.”

Official PlayStation Forums