Yeah, but 2nd (3rd, 4th, etc.) generation Legomaniacs are being born all the time. I have 3 boys, and the hardest decisions is who gets what. (Myself included.) A lot of kids still play with them, there will always be the ignorant, but when I go down the Lego Isle at a store, there are still quite a few kids, and adults buying for their kids. (Usually have to help them out.)
As to the actual purpose of this, if they made set it would be limited. Maybe make a UCS Lego Guitar, and some different Venues. I know my brother when we were growing up even painted a Lego guy with Sparkly paint, and built his own stage and band. So there will always be alittle market for it. I think the game looks funny, and the thing is that it will basically be Rock Band with a Lego theme as a game. Since myself and my kids love both, it is a perfect fit.