That's assuming BC is as important as it was when going from PSone to PS2 and from PS2 to PS3. I don't necessarely agree with this. From PS2 to PS3, PS2 games looked very dated compared to the newer generation titles. Much higher (progressive) resolution and a shift to HD plus the inclusion of a fully online network makes this last transition a much bigger one than what we can expect with the next one.
From this generation on to the next, we're not even necessarely expecting a jump in resolution. We might go from sub-hd to default 1280x720 - if we're lucky (and at the expense of complexity) we'll get 1080p. Due to rising costs, the economy and the success of alternative gameplay thanks to Move/Kinect, the jump in technology might not be as big as before either.
The result will be a smaller difference between this generation of games and the next. Sure, blockbuster games will be many times more impressive - but if you come to think of the fun and addictive games people have been buying en-mass though DD on live and PSN, they will not be as 'out-dated' on the new console.
A game like Super Stardust HD or PixelJunk Racers/Shooter whatever will be still as fun and fresh on the new generation of consoles and you can bet that even on the new PS4, you'll get simple easy games on the network that are graphically just as simple as what you can get now already. It is these games that are sold through DD that will be important that they run on new hardware (not so much the disc based games) - and these titles will not be as outdated like coming from the latest Medal of Honour on PS2 and comparing that with the launch gem RFOM.
Gaming has changed. PSone to PS2 was more sophisticated gameplay and higher resolution. PS2 to PS3 brought a standardised resolution (more or less HD), fully online compatible and an entire network to build up a social identity with trophies, interact with buddies and buy DD content. The next generation will only improve on the basis already layed. Who would want to start from scratch again in their right mind if you could have a continuous seemingless transistion?
Exactly!!