I more and more get the feeling it's mainly some sort of psychological thing that makes or brakes support of third parties. Most of them want to make movie-like games, push online and show how great they can make their games look on your system.
Maybe third parties are like gravity: You may not like it but it will always be there so why not arrange with it? Give them better online, a nice CPU and enough RAM and tell them they are cool. Epic will never stop bitching about Nintendo's systems but Capcom, Sega, Konami should be happy with these improvements. And with at least a one year headstart and a powerful-enough system they might just be happy enough to seriously support Nintendo's next console.
Look at the 3DS: Technically it is hardly more advanced than the DS was at the time of its release. All it needed was Nintendo saying "yeah, we're so hardcore" and a headstart and third parties went bonkers... once a good relationship has been established they will continue to support your system even with more powerful hardware out a year or two later. It's more about your console's image than the CPU inside it.