I saw this rumor myself a few days ago. A Sega youtube channel also mentioned the possibility that the Sega June 4th hardware announce is Microsoft related. Would be a smart move by MS to sell the system in Japan, Japanese consumers are hesitant to buy non-Japanese products, with the main exception being the popularity of the iPhone. By letting Sega sell it instead, they overcome that hurdle. Such a partnership would likely also mean that Sega games would all release on Xbox, including Atlus stuff, maybe even some timed exclusives, which could help to sell the console in Japan. Would Xbox light up the Japanese sales charts if this is true? Maybe not, but I think it could allow them to at least match the success of 360 in Japan (1.6m), if not exceed it somewhat.