At the beginning of every hardware cycle people make predictions on what the market will look like 2 generations out and I have yet to see someone who was particularly accurate ...
To a certain extent I see a consolidation happening and people may be heading toward a "single device to rule them all", which could (conceptually) be something like an iPad or netbook that has various forms of communication built into it. The problem with these multi-purpose devices is that they are necessarily generic which means that they tend to have significant user interface limitations; and they’re not particularly “agile” in the sense that they can’t rapidly change when there is a new market opportunity.
This is where Nintendo's (more or less) gaming only focus has their advantage; and, while I can't predict what they will do to compete against the devices of the future (that I also can't really predict) I do believe that they will find a way to offer something which can't (really) be done with these multi-function devices. As an example of what I mean, consider the 3D on the 3DS; while it is not (necessarily) a revolutionary technology, it can't really be done on a smart phone today (or a tablet PC) because changing the angle or orientation of the screen by too much eliminates the effect, and these devices operate under the assumption that users will constantly change the angle or orientation of the screen.
