No one is going to leave in the forseeable future. But the "most chances" to leave are microsoft's

I don't see any of them leaving the console market, but I do see Nintendo going 3rd party. After the Switch reveal, I just don't see them ever being able to sell more than 30 million units of any future device. They won't have the userbase to justify any 3rd party support, so they will loose any extra cash flow that being a manufacture brings. At the end of the day, Nintendo as a 3rd party is the biggest publisher in the industry. Nintendo as a manufacturer and making games for a microscopic userbase, is just a maasive waste of potential.

Sony and Micorosft are not going anywhere. PlayStation is Sony, the whole company rides on PlayStations success. It is the only brand/product/platform that can bring them to the front of consumer electronics. Sony TV's, Camera's, Phone, and Tablets, all depend on them making Playstation strong. Microsft will always have a TV box for games. The line between that box and a PC will get more and more blurry as time goes forward. I would not be surprised if Xbox gets rebranded as Surface Home or something in the future.

As long as Microsoft is moving consoles, games, and charging for online, I'm pretty sure they'll be sticking around.

Maybe Nintendo? I'd love their games on PC.

Definitely Microsoft, i get the feeling this will be their last gen.

PC,  they already basically all are lol. 

Why is this such a huge topic of discussion?

So it's like this existed for before the switch did.

None.

Microsoft, almost all of the exclusives they haven't cancelled yet are coming to PC, they're trying to convert all Windows devices with the same adaptive shell design and universal app platform, including XBOX. The Scorpio will probably use AMD's new cards and that will be cheap enough by the time of it's release that they can sell it for a "reasonable" price, but it's basically going to be a more expensive pre-built PC without the modularity, x86 software and paid online. It isn't really selling well either, so Scorpio will probably be the last XBOX.

People talk about Nintendo being next in line, but I'd heavily disagree, they have an ocean of money reserved, and they aren't lacking ideas, games nor buyers. They will go third party if they fail in every aspect and loose their entire fanbase in a 100 years. If anything Nintendo will be the last man standing in the world of consoles.

I mean that this isn't an original or timely topic. I've seen dozens of threads asking literally the exact same question since I started posting here. So I'm wondering why it's such a popular question to ask.