According to this article, the bass support will not be available to the US until it comes out as DLC. For me, it's not good because I don't have a guitar and I'm not interested in playing guitar but I will have to buy the standard game and then buy the DLC. I probably will buy it anyway, but I won't be happy about that extra cost. A separate release would make me much happier, or the combo of the two without additional cost (free DLC for the ones that already own it), Who am I kidding though, it's all about the extra money.
http://theherofeed.com/4053/rocksmith-bass-content-to-be-on-disc-with-europe-release/