They kept developing on Xbox 360 because it was easy to develop and the one year headstart made them more efficient on that. Of course that CELL didn`t help change that.
My guess is that for now they will not risk big budgets on smaller platforms and go with they are good at and is less risky.
If they go already for PS4 and X720 development - to actually take advantage of it - it might be a big risk. Specially if it`s a new IP.
It won't be a risk if they already know how to do basic coding on the Wii U, a big reason I have no issues with developers starting off with ports of older games, it allows them to earn their chops on the platform and test the market with their offering.
When they do take advantage of the 720 and PS4, it will be in terms of world size, and LOD. It may come in the form or more polygon rich models but most developers will probably refrain unless they are going for something specific because they'll know it won't be worth it given the law of diminishing returns and how it applies to computer generated 3d models.