The argument is that digital content is now expected to be portable across compatible devices, such that your iOS game runs on both your iPhone and iPad. Though I agree expectations are headed that way, I don't think it's ingrained enough to affect next-gen yet, because:
1) Software isn't completely portable. It's possible to buy software for a device and find it doesn't run on your new device.
2) Consoles have a history among the gamers who use them of leaving the old stuff behind.
Joker's point about new users, like Kinect users, maybe has some merit. Perhaps they'll be miffed if their Kinect software doesn't work on XB3? Then again, perhaps they'll be too busy playing Kinect 2 stuff, or even waiting until the price drops because they aren't hardcore enough to want a new console from day one at full price? And that situation doesn't affect the other console either. People won't migrate to PS4 because Kinect games no longer work on XB3. PS4 won't lose customers to XB3 because Move games don't run on PS4. You may slow hardware adoption as people wait until the software they want is there, but that's key to any new platform anyway. Hence the idea that whatever money could be spent on BC should instead be spent on creating a next-gen experience that people will want enough to leave the old experience behind.
1) Software isn't completely portable. It's possible to buy software for a device and find it doesn't run on your new device.
2) Consoles have a history among the gamers who use them of leaving the old stuff behind.
Joker's point about new users, like Kinect users, maybe has some merit. Perhaps they'll be miffed if their Kinect software doesn't work on XB3? Then again, perhaps they'll be too busy playing Kinect 2 stuff, or even waiting until the price drops because they aren't hardcore enough to want a new console from day one at full price? And that situation doesn't affect the other console either. People won't migrate to PS4 because Kinect games no longer work on XB3. PS4 won't lose customers to XB3 because Move games don't run on PS4. You may slow hardware adoption as people wait until the software they want is there, but that's key to any new platform anyway. Hence the idea that whatever money could be spent on BC should instead be spent on creating a next-gen experience that people will want enough to leave the old experience behind.