Here's the thing about new console generations. Console's jump a generation for only two reasons.
1. There is a big enough leap in video game tech to warrant a need for more powerful hardware in a home console. For example when we jumped from sprites to 3D based gaming, consoles needed new tech to support that new graphical need.
2. The existing generation of consoles has been streched to the breaking point where game developers simply cannot continue to advance the industry on the old hardware. This is why the PS3 and the X360 lasted for so long. Both Sony and Microsoft didn't want to push out new consoles when games were still progressing on that generation of consoles.
Notice how each new generation has started to reduce the bump in graphical fidelity. There are still some last gen games that look pretty freaking great. Final Fantasy 13 is a good example of the kind of graphical power capable by those systems. Generation 8 has been more about performance more than graphics, trying to get everything to run at 30fps locked has been a challenge because both systems tried to get away with undercutting the hardware.
Thus you have the Scorpio and the Pro, same generation of system, with a enough power to at least hit those 30 fps minimums.
As a result I doubt we are anywhere near something that could be called a "next generation" of system. Video games have kind of reached a graphical peak if I'm honest. Think of the best look games out there, it would be really hard to top that. Sure could we get more graphically amazing games? Yes, but I don't think that the investment in time and money to make that happen is really feasible now. The video game market is only so big, and revenue from a game doesn't go as far as a major film, so the investment can't be as high.
Honestly I think there wont be a next generation until something comes along that requires it. Maybe once developers figure out how to really do full AAA VR games. I could see VR being the driving force of Sony and Microsoft having to push out more powerful boxes beyond the Xbox and the Pro.
But I still think that's at least 5 years off.