No not and ERSB rating, already knew that would be T, but they rated the difficulty for the songs that are coming out on the disc at launch date. They also were nice enough to break it down by the different categories as well as overall band. No listing of how difficult, like on the current Rock Band Store, but early images show that is how the songs will be sorted out and displayed from the get go in the game. But at least here, you can prep yourself for what is to come.
I do like seeing Tenacious D down in the ranks of Megadeth and Judas Priest in the level of difficulty. Thus proving that those two guys do rock as hard as they say they do. Well at least according to Harmonix.