Update: False alarm.
The news is the public launch of the Rock Band Network Music Store. Get more info at Billboard.
Original Story: Some "huge" Rock Band news is incoming today, according to the game's official Twitter.
The tweet that contained the info said:
You best be following @RockBandtoday if you want to get some HUGE news!
The only question is what could be? Either the formal announcement of Rock Band 3, or the inclusion of a really big band with substantial DLC [please Jesus, OK Computer by Radiohead - JC]
For now, the only Rock Band game known to be in development for this year is Green Day: Rock Band. A specific date is yet to be tied down.