According to nintendowiifanboy the five bonus songs have been revealed.

• "Dirty Little Secret" - The All American Rejects
• "Roam" - The B-52's
• "Don't Look Back in Anger" - Oasis
• "Roxanne" - The Police
• "Rockaway Beach" - The Ramonese

So they're not anything tailored to Nintendo's fanbase and they are just random selections of DLC already available on 360/PS3. While it would have been nice to get some DK Rap in RB these songs are ok I guess. I still don't plan on buying RB though until the GHIII guitar is supported. Every GH game has had a regular controller (PS2, 360, Wiimote) alternative to guitar control. Why don't they just set it up so you use the Nintendo classic controller. It sends the exact same calls as the Les Paul and therefore it would work.  I don't think Activision/Neversoft have any rights over classic controller usage.

http://www.gametrailers.com/player/32808.html

That's the link to the Nintendo Media Summit Interview where the songs were revealed. Nothing else interesting in there really. Talks about no DLC and USB hub for the instruments so no wiimotes needed.

If it doesn't support GHIII guitars it will fail, and by fail I mean not selling 1 mln.

A long time ago I had interest on Rock Band, but the way EA is screwing pal gamers (especially wii owners) I dont wanna touch it. Samba Di Amigo FTW.

 Not getting a million wouldn't be a failure.  Getting close or beating it would be a huge success.  The PS3/PS2 combined haven't sold a million so a version coming out months later would probably have lower expectations.  Plus 360 GH beat Wii GH and the 360 RB is at 1.18 million.