Nintendo will improve the graphics on the SuperWii, I don't know if they'll be better than the 360, like Squilliam said. Nintendo will try to do a low consumption and not so expensive console. If the technology's cost allow it, they will, we still don't know how many years left are for the next Nintendo console.
But even if they use HD or not, the graphics are not their main priority. The big success of the Wii over the other consoles is in part because graphics became a comodity. Nintendo is already trying new things. Microsoft and Sony are the ones to follow Nintendo's strategy, not the other way.
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