Gamasutra Sez: Sonic Co-Creator Hirokazu Yasuhara Joins Nintendo
It's not clear what role he'll have with the company. It's believed that he's joining Nintendo of America (possibly Nintendo Software Technology).
Considering some people's reactions, there is one thing I would like to make clear, though. This has nothing to do whatsoever with Sega or the Sonic the Hedgehog franchise. He left Sega more than, if not a decade ago. The article even mentions that he had previously worked for Namco Bandai before he went to Nintendo. Personally, I don't know what will happen next, but for now, I'm going to assume that some good will come out of it.
Cartoons aren't "just for kids"...but they're not just for adults either. They're for everyone.