"Risen 2 will be using Steam, respectively Steamworks as copy protection. This applies to all PC versions, including the boxed version available in retail stores. The decision is on a world wide basis, it will be the same everywhere on the planet. Local distributors will not be allowed to offer Steam-free versions with alternative copy protection systems."
BTW, the PC disc retail version is still listed, but not available until May 22. Whether or not it will be canceled is not confirmed; and it seems like it depends on the dealings between Deep Silver and Square Enix.