The new campaign will take place between the current "No Mercy" and "Death Toll" campaigns, and is expected to feature new locations, fresh dialogue, an explosive finale, tweaked item spawning and a recharge timer for infected teammates. Gamers who play on the PC version of Left 4 Dead will be able to download the update free of charge via Valve's content delivery system, Steam. The unfortunate souls playing on the Xbox 360 will have to shell out 560 Microsoft points for the content - or about $7.
You can take a look at the new campaign's movie poster at Shacknews. Hopefully this will please the now 41,000+ "boycotters" of Left 4 Dead 2 - but, somehow I doubt it.