2K Games has said Borderlands 2 will ship with Steamworks on PC.
You will also be able to use the Steam Cloud service, and all the other nifty benefits which come along with the DRM people seem to like better than most.
This means: Steam Achievements, auto-updating, multiplayer matchmaking, ease of access to DLC and all the other benefits whether its a PC retail version or you purchased the game through Steam.
Pre-orders are now being accepted.
Borderlands 2 is out September 18 in the US and September 21 in Europe.