Whether Apple would even need to buy or merge with Nintendo is more the question.
More likely Apple would create a partnership with a company like Nintendo or steal their programmers to insure games that could function on an incarnation of the iPod. Rememer there will come a time that the iPod will start to lose it's grip on the majority of music mp3 players and video is still not settled as to download legality issues.
Some have mentioned the use of the mini as a gaming console. Perhaps if the graphics cards were optionally upgraded it would make sense. But my main question would be how this would jive with the ability of the Mac to now run Windows. Why bother if all you need is a copy of XP or better to run all the PC games? I could see this happening before the switch to Intel but why now?
But who knows? Steve has surprised us in the past. Maybe he has a home play center in mind and games are part of it.
