The Witcher 2: Version 2.0 will release September 29, CD Projekt RED has announced via an automatic update.
The following features are included in the update- a tutorial system, a new difficulty level called Dark Mode, 20 new enchantments to your character (unspecified), and an Arena Mode which will see players fight waves of enemies in an arcade like mode.
The Xbox 360 version, which is due for release next year, will release with this update included already. A new trailer for the 360 version is given above. Enjoy.