There is no way Sony and Microsoft can make the Wii U look like the Wii unless the want to spend millions of dollars and sell the consoles around $1500-more at a loss which won't happen.
I don't think the graphical differences will be nearly as great as it was last generation, but I do expect Nintendo to be last again in terms of graphics. And both kind of have a track record at selling consoles at a loss, I expect them to do the same thing again. I'm on Nintendo's side, as I hate the other companies' stances towards gaming, but I just call it as I see it. Nintendo's machine will be underpowered again by both consoles. Maybe not by much, but I do expect to see a clear difference, at least on some titles.