GameRadar.com set up an interview with Chet Faliszek, who is a L4D2 dev. Below is a list of some questions that where asked. The questions will give you a good idea of what to expect from the upcoming release.
Be advised that there in the article there are some spoilers for the end of the ‘Dark Carnival’ campaign inside, so you may want to skip ahead when you come to the warning.

Where did the New Orleans setting come from?? I think quite a few people came up with the idea of swamps. It grew from there to New Orleans. We had the idea that the different cities of the world are not all dug-in fending off the zombie apocalypse. They’re all at different stages, and we’re trying to explore that.
What can you tell us about the different campaigns? There’s The Parish, which is the New Orleans French Quarter. We’ve shown the beginning of Swamp Fever. The swamp is a very creepy area. I’d lived in New Orleans for a little bit, and I think people were surprised how much stuff is actually in the swamp. It’s not just trees and moss and water. There’s a lot of weird things, so it ends up being this cool place with little villages along your route.
Left 4 Dead 2’s new maps have alternate routes the AI Director can open up. How do you stop this becoming confusing for players? One of our first thoughts on this was: the best thing for replayability is a random map. But it ends up exhausting for the player. You want some things you know, because otherwise you’re always being reactive, and we find players want to be strategic. They want to think about it as they’re playing – be able to go, “Oh my God, that’s happening there, we should run back here.” With that in mind we’ve balanced it, where only sections of certain maps play differently each time. And that’s based on how you’re doing. The Director’s deciding ‘should I make the path longer, shorter, or a little bit more difficult?’
Why did you decide to focus on adding melee weapons? It’s a classic horror film thing, it’s a classic zombie thing. You pick up what’s next to you and you smash the baddie in the head. There’s a lot of fun things you can use to hit zombies, from Gordon Freeman’s crowbar to a guitar. Chainsaws are something you have to have in a zombie movie.
Beyond melee, what other new weapons are you adding? There’s the Boomer bile you can throw, mainly in the first campaign. It’s an alternative to the pipe bomb. We have a multitude of rifles available. The classic assault rifle from L4D1, a new one they used in Desert Storm that fires in three-round bursts, the AK-47 that’s really good up close but not so good farther away. There’s multiple pistols, including a magnum which is super-powerful up close. We wanted to give you a bigger range, so you can choose your style. For instance, the grenade launcher... it very much changes your style of play. You can’t shoot too close to your friends because of friendly fire, and what do you do if your buddy has been jumped on by the Jockey? Take him out too, or run up with a melee weapon?
Can you modify those weapons? You can pick up a modifier to add a laser sight that not only lets you see where everyone is aiming – which is really helpful – but also helps your accuracy a bit. You can tie that with the AK-47 and you’ve got this really cool weapon. You’ve got ammo upgrades, like incendiary ammo or explosive rounds, and you can carry that with you and decide when you want to play it. There’s a bit of deploying time, so you have to be strategic when you want to pull that out.












