If Nintendo were to buy the Xbox division, Xbox One wouldn't be the point of it. Like you said, they'd get Rare back. Also, they'd get Halo, Project Gotham, Fable, Gears of War etc. They would also get Xbox Live, that infrastructure, and a **** ton of patents. That's where the value lies. Anyone who thinks, "They can just replace Wii U," isn't thinking outside the box. Nintendo would be taking all those assets for the purpose of applying it to future hardware.