From the sticky on the front page:

Planned features for release
More maps: e.g. pier, office, something BIG, and something even BIGGER!
More weapons/items: Tranquilizer pistol, some tools of the trade.
Improved graphics system: needed to fix few bugs, increase stability, and to make the game look shinier.
More audio and SFX.
Map editor / support for player made maps. (Steam Workshop)