As others have said, if Xbox remains profitable then they'll stay, if it doesn't remain profitable....not sure. Sure, MS stuck out with the original Xbox, but given its main job was to establish the brand and get a foothold in the market, investors were prepared to wear the multi-billion dollar losses. X360 was overall profitable and much more successful for them and so investors were happy, but if (and thats a big if) Xbone is unprofitable for an extended period (say 2 years) then MS may experience growing pressure from investors to spin it off.
Investors want return on investment. They started to get that return on investment during the 360 days, but if that goes the other way with Xbone then they may pressure MS to cash out of the business, especially if the industry starts to decline. Not saying MS should, but the herd mentality of investors is all about short term gain, not long term growth.







