It was only a matter of time but it seems that Satoru Iwata could sit by no longer as the current situation with Nintendo and the Wii U has gotten progressively worse over the last 3 months. It has been apparent for quite some time to many fans in NOA that a change was needed when the Wii U was announced in 2011 and that the company has been disconnected with North American fans and new consumers alike. Combine that with next to no games for the Wii U for 2013 until the end of March and it's easy to see why this happened now.
Iwata would like to combine efforts of Japan, North America and Europe more seamlessly and able to get one clear message to all consumers and not many convoluted messages to different territories. Localization is probably one of the big issues to tackle, not to mention advertising and approach. Iwata admitted in the recent investors meeting that Nintendo failed to make a clear distinction about what the Wii U was and this led to many thinking the console was not a console but just an add-on to the first Wii system. While Iwata actually stated that Nintendo themselves is back making profit, they have a huge challenge ahead in getting momentum started with the Wii U.
While many of the issues with Wii U's launch could be directly blamed on Iwata, one can't deny that Reggie has not been a very good President of NOA these past few years and some of his recent comments and blunders haven't been any help to the company. Reggie will continue was NOA President (in title) for now but one has to expect that he will be out in the not too distant future. Change can be good and it looks like this change has the potential to be very good in the long run. I know many people (including myself) were hoping for Nintendo and Iwata to shake things up a bit at Nintendo headquarters.