The pack will include one level, titled "Foundry," along with two new weapons: the AK-47 and katana (pictured below, left). Tripwire is also planning to release a paid DLC pack soon, which will include "four new playable characters including a Horzine foundry worker and a soldier in prototype Horzine body armor."
The Katana kinda reminds me of Deus Ex's Nanoelectric Sword... which could mean total win as that was the most awesome melee weapon ever and just about the only weapon I used in Deus Ex and somehow that quite possibly only made the game better, lolxD. Shall see though as sneaking-up on zombies in KF isn't quite like getting behind guards in Deus Ex ;)
Anyway, more stuff for KF is always welcome.