Left 4 Dead 1.5, "Here's how it should of been". A game assumed to kill of Left 4 Dead, seeing how in the eyes of Valve, Left 4 Dead is an old man because it dropped to 30 dollars in retail stores. Left 4 Dead 2 is a "DLC that was too big" says Valve, so instead they decided to release it as a full game and slap a 50 dollar tag on it and pretend Left 4 Dead was never released. It would be great to have a silenced uzi in a zombie apocalypse wouldn't it?
L4D2 player: "Am I play Left 4 Dead or Left 4 Dead 2?" *looks at Left 4 Dead 2 CD case* "WHAAT?!"
Valve: So, I heard you want some DLCs from us? Since when did we promise DLCs for Left 4 Dead? *Person shows previous interviews*.
Valve: LEFT4DEAD2 DESERVES TO BE A SEQUEL, I PROMISE! OR....I'LL TRADE YOU DLC FOR 50 DOLLARS!