You kids can stop biting your nails now as Harmonix has confirmed everyone can export Rock Band 2 disc songs to Rock Band 3. More details will be known later in September (including a few tracks that can't be exported) but they've also shared a couple of interesting details.
Harmonix appears set to update legacy songs with Rock Band 3 features like keyboards, Pro Mode, and maybe harmonies. Aside from older Rock Band Network songs not supporting keyboards, Harmonix would like you to kindly request what you want to be updated at the RockBand.com forums but to also be very patient because "it's a lot of f***ing work." The Beatles: Rock Band content could also be updated but there's nothing planned at the moment.
Setlists, accomplishments, and other Rock Band 3 activities you want the world to know can be published to Twitter and Facebook. Simply link your game to RockBand.com and then tie your Twitter and Facebook account to it. You can set how much can be posted so you don't spam friends to the high heavens.
Those looking toward getting their own Fender Mustang guitar for Pro Mode will be pleased to know it's compatible for the standard five-lane gameplay. As for when you can get your hands on the six-string Fender Stratocaster, Fender is doing their best to get it out at the end of the year but there's a chance it'll go into very early 2011; pricing will be close to what an actual Stratocaster is worth.
Lastly, Harmonix flips the bird at you 70,000 schmucks who thought Rock Band 2's "Bladder of Steel" achievement was an easy grab: Rock Band 3's "Obsessive Compulsive" will present a true test of dedication. How do you get it? "Play every note in Rock Band 3." Interpret that as you will.
Update: More bits of info are out, most importantly about Pro Mode and DLC: Harmonix doesn't want to raise prices on players who don't want Pro Mode charts in their DLC so Pro charts for Guitar and Bass are extra. However, you will get your money's worth because Rock Band 3 includes a modifier to show tablature and finger placement for these charts.
Animation style for characters (Rock, Goth, etc.) has been taken out; each song will dictate the proper style your avatars will be jamming to instead. On the plus side, everyone will be looking sharper and all clothing styles from past Rock Band games are present so you can recreate your favorite character.
For stat buffs, the score results screen adds tons of details like accuracy, streak, overdrive, and solos. You can even see how one member did compared to the rest of the band.
There will not be a big, epic bundle that throws every instrument into a single box. Retailers don't like big boxes and not many will have a need for it. Buy your instruments individually or be on the lookout for sales on older bundles.