It's a lot easier to port up than to port down. It's a lot easier to make something run on hardware with more power and resources than it was designed for than to adapt it to working with less. In addition to that, there are certain technical things like the Wii just couldn't do, and had to be worked around.
This is why I'm more confident in support for the Wii U than I was for the Wii. The Wii U is built with standards in mind, as opposed to the proprietary graphics tech the Wii used. Also, stuff like game engines are a lot more scalable now than they were in the past, largely due to the rise of mobile devices. Even if Orbis and Durango are as much more powerful than the Wii U than PS3 and 360 were over the Wii (which I don't think they will be), it should be a lot easier to port things down to the Wii U because of the much more developer-friendly way Nintendo designed it.