http://www.rockpapershotgun.com/2009/06/01/left-4-dead-2-exclusive-rps-preview/Yeah. Not a Left 4 Dead update, an entirely new game. And it looks to be
exactly the same as L4D1, just with more gore, weapons, special infected, and features. Which means everyone will be playing that instead of L4D1. Which means that shiny new game you spent fifty bucks on, the one Valve looked to be shaping up into the next TF2 with updates, will be obsolete come November.
Granted, the new content does look pretty awesome. But it's extremely obvious Valve could have incorporated all of this into the existing framework of the first game with varying degrees of effort. I mean, you don't see them putting out a brand-new Team Fortress every time they want to update a class, do you?
So until and unless this is either a prank, or secretly an expansion to L4D1 (neither of which is out of the question, mind you), I'm calling shenanigans on Valve.