Yep, if you're interested in commercial releases for Xbox360, there are two options, a) build your prototype and go to a publisher with it (traditional way) or b) wait for the already announced v2 of xna game studio express as it's likely that they will address this in the new licence too.
Some info can be fount here http://creators.xna.com or in the blog http://blogs.msdn.com/xna/archive/2007/08/13/announcing-xna-game-studio-2-0.aspx
Some info can be fount here http://creators.xna.com or in the blog http://blogs.msdn.com/xna/archive/2007/08/13/announcing-xna-game-studio-2-0.aspx