Maybe I am in the minority, but once PS3 came out, I lost all interest in playing PS2 games. I have a feeling that when the PS4 comes out, there are going to be cool new games to take my interest from my PS3 games. Same goes for my XBOX. I don't think I have played a game besides Counterstrike/TF2 that hasn't come out in the past yea for my PC either.
More like silent majority. Most people will move on completely.
Some people will say that BC is primarily for at launch when there aren't many new titles, but given how focused people will be on the new games I think the BC doesn't really come up until later on when there's a rut in new releases. It's nice then to just have one box and still be able to play some old games, but I think most people just don't care. Given the variety of architectures used over the last couple generations you either have to significantly increase cost to include old hardware, or try and overpower it through emulation.
Most of the time when backwards compatibility is super important for someone its just for one or two games, maybe a handful, in which case I wonder why you can't just hold onto the old console.
I am personally less interested in having just one box and more interested in access to some of these games when I just get an itch to play them one day, even though I usually don't get very far into most of them before quitting. The really old stuff is ok, but the current generation is so (relatively) prone to failure you never know when you might be locked out of your catalog of games. Despite my huge backlog of games from Steam sales, I still periodically pull out an old console or maybe an emulator to play through something. But if I just didn't have them still I probably wouldn't think on it so hard. I also enjoy too many different types of games, and I've been gaming across multiple platforms, including PC, since the NES era, so there's too much to spend a lot of time going back, even if I only pick out the best.