Your words not mine .

Nintendo and MS drop out
Sony sells PS and whoever picks the reigns gets a monopoly

I don't know if it's really accurate to even call it Gen 9. I think all three will go in directions that end what is traditionally considered a generation.

But first, let's get the ridiculous notion that Microsoft will phase out the xbox. No. I think that they will try and turn Xbox into a Steam like service. They will release new Xbox branded products, but instead of running unique xbox firmware, it will use Windows. Basically, it'll be the Steam Machine, but Microsoft endorsed and running the same software as their PC variant. They will likely follow Sony and allow players to stream games they own as well.

Nintendo, well I think everyone is well aware of my thoughts on the NX.

Sony will go with PS Now for its future. It's building the library now with legacy titles. By the time the PS4 is being phased out, it will have a plethora of PS1, PS2, and PS3 titles, and will have streaming issues ironed out. The pricing model will be tweaked, and they may even have a good handful of PS4 games on the service. They'll start to release PS Now "exclusive" games, which will really be what many of you would call "PS5" games, and the machines powering the games will be upgraded to match the power of modern PCs of the time. Sony may release a small streaming box at that time called the "PS Now TV" for people without TVs, and it'll likely be cheap, around $100 or so, but most people will just play their PS Now on their Smart TVs, so it won't sell astronomically.

All three will be successful, and the weird sense of competition amongst fans of the three will die out because there will no longer be a huge financial barrier to own and enjoy multiple brands. You buy the NX, subscribe to PSN for cheap, and subscribe to XBL for cheap. Games are finally one big family. The apocalypse ends the world the very next day.

Please buy Arbys.

I think Nintendo's next console, the NX, is going to compete with the current ones. By 2020 we should know about the PS5/XBtwo and also the NX2.

I think enough people want disc based consoles still that it's worth having the option.  If they want a slightly cheaper ($50 probably) version with no disc drive then they should be doing that with PS4.  I think in 5 years we'll still have plenty of people that want physical media

Microsoft: Out of the three console manufacturers they're the most volatile of them all and it will be uncertain if they can retain the power of their current IPs to build a foundation for the next generation ...

Nintendo: The NX will not be the competitor to Sony or Microsoft next home platform. That should be the NX's successors job and there's too little data to know whether or not they will succeed ...

Sony: The most obvious candidate to continue to hold it's place since they've shown to make the least amount of mistakes ...