Neither the XBone or PS4 are going to tank, they're both very capable machines with a strong following. They're profitable now (indeed, have been for 5 years) and it'd be an awfully long uphill battle for anyone else to enter the market. With the WiiU sales being crap it's basically down to a duopoly, you really think Microsoft and Sony want to go on an all-out price war for your benefit? No, you'll be paying enough that both enjoy a comfortable profit margin. Ten years ago the gaming division was a huge money burner, today it's a money maker. If Microsoft wanted to sell their gaming division, how much more could they cash in than 10 years ago?
For long-running businesses that have a steady cash flow the stock market has usually put a P/E ratio of 10-20 on it, that's price to earnings and currently Microsoft as a whole is at 12.59. Last fiscal year the gaming division earned $380 million, so if we take the average P/E it's probably worth around $380*12.59 = $4.8 billion while the money losing division ten years ago was probably close to unsalable. So if you include that Microsoft has actually turned a profit in the last 10 years, it's just that most is still in their pockets as an asset. If they really wanted to, they could almost certainly sell out the division for more than those $3 billion.