Harmonix will produce no new DLC for any Rock Band game other than Rock Band 3.
It doesn't matter if the songs are labelled "RB3 version" or not, Joystiq discovered - they won't work with older games in the series.
Harmonix's defence? That there are new authoring standards, new instruments and new in-game venues and lighting to program for. The new content is simply incompatible, it seems.
However, the community may still create songs for older Rock Band games using the Rock Band Network.
Rock Band 3 owners can import old songs from the Rock Band 1 and Rock Band 2 discs for a fee. Existing Rock Band DLC can be played in traditional gameplay mode, but there's an added charge if you want to enable keyboard and vocal harmony parts for the song - or if you want the new Pro Guitar and Pro Bass parts.
The Pro Guitar and Pro Bass versions of the recently added Bon Jovi DLC don't appear to be available yet - can you see them?
You won't be able to play them, however, until the life-like Rock Band 3 Wireless Fender Mustang Pro-Guitar controller (aka Pro Guitar) arrives in shops at the end of the month. When it does (and presuming you have Ł125 spare to buy it), you can actually teach yourself to play the guitar using Rock Band 3 exercises and tutorials.
That's one of the reasons Rock Band 3 is the best music game of its type we've ever played. Resident Steps fan Johnny Minkley reviewed Rock Band 3 for Eurogamer.