No-longer affiliated with MTV, Harmonix’s Rock Band 4 ships later this year. Mad Catz is making the instruments and old DLC will be compatible. Most likely just from one console generation to another as opposed to cross manufacturer. They’re working on instrument backwards compatibility. No Wii version. That Penny Arcade guitar is possibly the most hideous peripheral I’ve ever seen.
Rocksmith still seems more interesting to me, though it isn’t a party game at all.