If you could run a particular Durango game on Wii U at 720 p vs. 1080 p at 30 fps with relatively minimal loss of detail (at least foreground detail, things may stream in closer up in open world games), good lighting, and still have decent texture quality. That would be flattering.
I could be wrong but I think most devs will either not bother with ports or they will be substantially downgraded. Sub HD, inconsistent frame rate, slashing details/object density, substantially lower texture resolution with pronounced texture streaming, tearing, dramatically reduced lighting.
Why would I even come to such a conclusion? Because so far, none of the ports from the previous gen are doing anything visually impressive thus far and we even have reports of some big ports currently looking like ass. So, if they are willing to show that, I really have no hope for ports from machines 10 times more advanced :/