Don't want to get into an argument, but if every song is basically just a file with some audio, animations, and some beat-matching midi stuff, couldn't they just write a batch conversion tool to convert everything to their new format?
Not really. Your first problem is that RB1 disc exports, RB1 DLC, RB2 DLC, RBN DLC, and RB3 DLC are
all different file formats, and Harmonix's main challenge with each new RB game has been to make a new engine that can support all of those at the same time. The RB1 export, because it was planned at the last minute after fan requests, actually does some weird fucked-up thing with save files (which is part of the loophole on how customs were able to be added in.)
Your second problem is the legal rights. Harmonix is already making an effort at getting RBN songs back in RB4 as seen through that 30-pack of songs from pre-ordering through Amazon, but they would be a legal nightmare to deal with, not to mention the fact that the original developers of RBN songs would legally be the ones who had to do the work updating the songs for RB4 - and since RBN was pretty unanimously a financial failure, nobody really wants to do that. You may see some come back on a per-song basis, but don't hold your breath that "Dreaming of Demon Hell Death (2x Bass Pedal)" by the garage band across the street is hitting RB4.
We actually already saw a similar situation to this with the Wii release of Rock Band 2 - Harmonix went back and ported every last DLC song in their catalogue, a new batch of old DLC per week, until every single song had been ported to the Wii. It was something like fifteen songs per week. We'll probably see something similar here.
Sorry if this has been answered, but have they confirmed whether you can use the PS3/360 MIDI adapters on the new consoles?
Or will at least offer a new one? I have MIDI drums, and there's simply no way I can go back to the plastic garbage.
Nothing said on MIDI adapters one way or another, just old controllers.