In addition, Kotaku reports that EA said that a European release of Rock Band was set for April-June of this year "across all SKUs." You know what's a SKU that, as of right now, has a version of Rock Band? That's right, the Wii. So we should probably expect the Wii game in the U.S. around the same time.
Of course, there are no details, so we don't know if it's going to have all of the amazing features of the "next-gen" versions, or will be more like the still-awesome PS2 version.
[Thanks, Tanks and Smit!]