Here's my observation ...
Most games that have been released for the HD consoles and run at 720p@30fps with 4xAA will run with with significantly higher detail and better effects at 720p@30fps with 8xAA on a graphics card that was 3 years old and cost (roughly) $100 when it was new. To play these same games at 1080p@60fps with 8xAA while maintaining this same level of detail and effects requires a fairly high end modern graphics card; and if you were going to push the effects you see in tech demos for next generation game engines at these resolutions you would need several high end graphics cards in your PC.
Why this is important is it demonstrates that there will (probably) be (essentially) two approaches third party developers can take in the next generation if there is a significant processing power difference. They could probably develop games for the Wii U targeting 720p@30fps and then release enhanced versions that run at 1080p@60fps on more powerful hardware, or they can push the latest and greatest graphics at 720p on the more powerful hardware.
In my opinion, with the "better graphics" approach translating to higher development costs and a smaller potential userbase it will likely be used on a limited basis unless the more powerful consoles sell remarkably well.







