Nothing, it's a silly concept that only works when companies release consoles at relatively the same time as each other, which isn't happening with the NX.

To me, a generation is a construct whose meaningfulness depends on its intuivity. It's useful when it can be defined intuitively, but when it can't be it's useless and shouldn't even be tried to be defined. That is, with the current direction the industry is taking, the concept of a generation is becoming less and less meaningful.

The traditional generation thinking can be expanded a bit by talking about a console company's own generations, but it's becoming harder and harder to divide all consoles into generations. This is because the release times aren't so periodic anymore, and the consoles themselves seem to be taking different directions. And even the division into each console company's own generations could become problematic as the release cycles become shorter and each console iteration is closer to the one before it, including high compatibility with its predecessors.

So yeah, it's becoming a useless construct.

LOL - by that theory Wii U is generationless because I can play NES SNES N64 Gamecube Wii gameson it

digital remasters, not your previous cartridges. And you cant play Wii U games on the Wii 

People like me. (Fanboys)

When Sony releases a new console.

This.

Exclusive games with a decent bump in power compared to THE COMPANY'S previous gen. The NX will have its own unique features, games, and services when compared to the WiiU. That is what makes it 9th gen.

The Neo is a slightly more powerful PS4 with no exclusive features, games, or services. It will run the same games but at a slightly higher performance level. That is what makes it 8th gen.

Not that hard...

LOL at you, you just have to read. He gave a good definition that works for your example. The Wii U play NES games, but the NES don't play Wii U games, not to mention incompatibility for accessories, so they are different generations.

Anyway, it could be the end of the generations as we know them, but in this case just like the PC, it will rise some questions about compatibility. I can't imagine developpers keeping full compatibility with hardware more than 10 years old. Which means compatibility between PS4 and PS4.5 would be lost at some point.

I've always viewed it as the next in line. As long as it was new hardware and not an add on for the current or previous system, then it's the next generation of that brand's console. The confusion occured when people started using the power of the machine as the basis. For example, people have said that the Wii U is competing with the 360 and PS3, but in reality, it is part of the generation with PS4 and XB1. 

Interestingly, we are approaching/are in the digital era, where streaming is feasible for many and content can be purchased, obtained and played from the comfort of one's home. This has console developers thinking about ways to cash in on that with minimal expense, such as ending the era of the physical console, and leaning towards PC based apps like Steam.