Revealed through a trailer on g4tv, Harmonix has announced their new Rock Band title in over a year called Rock Band Blitz. Similar to the Rock Band Unplugged for the PSP, Blitz will be based on the developer's prior experience with Frequency and Amplitude. So instead of using instruments, you will be switching from track to track in a single-player experience.
At first glance, Blitz seems a little simpler than its predecessors by the fact that there are only two nodes on a track as opposed to three. But it does appear that the speed is markedly greater and that the types of power-ups could be more complex. And it seems that Blitz will at least retain the psychedelic styling of Amplitude. (I'm in need of a mindtrip right now.)
Luckily, all of the DLC you've purchased for the Rock Band series will be compatible (for me that's over 500 songs), which means that over 3,700 songs will be available in addition to the tracks already included in the game. Players will be able to see their friends' rankings through leaderboards and will be presented with several recommendations for additional DLC songs they may want to include.
Rock Band Blitz arrives this summer for PSN and XBLA. No word on price just yet.