A the company's PAX panel, Harmonix Project Lead Chris Foster asked, "We've said Rock Band 3 would have harmonies already, right?" His fellow panelists responded "No!" Cat's out of the bag now, though, eh?
Green Day: Rock Band will also offer vocal harmonies.
I expect many more game enhancements in Rock Band 3. My wish-list: A drop-in/drop-out party mode like Guitar Hero, a super-easy mode (you know, for kids!), and here's a couple crazy one: Key-tar peripheral and support for actual MIDI guitars. What about you? Do you have any suggestions/wants for the next game?