The NES was redesigned to be top-loading, but this was after the Super NES was already out for a while so I think it's pretty rare.
There was also a redesigned Super NES, slightly sleeker, which is also rare.
Later N64s came in different colours, and there was also a Pikachu N64, but I doubt any of those are common either, and these redesigns were mostly just aesthetic as far as I know.
GameCubes always came in different colours, but later GameCubes had the component output part omitted because Nintendo didn't think anyone used it. (I do, but I guess I'm in the minority.) (Not enough people bought the Panasonic Q version for that to be relevant, either.)
All these console redesigns came late in their "lives", shortly before (or in the case of the NES, after) the release of the next generation console. (With the exception of the Panasonic Q, but whatever.)
So we could very well see a redesign of the Revolution, in fact it's likely, but if the past is any indication, we'll be salivating over the possibilities of the sixth Nintendo console before a Revolution Revision is available.
In other words: I wouldn't hold out for a later one, it doesn't seem worth the wait. Handhelds see more revisions because portability and visibility (and style) is more important on the go.