For it to be a "PS4" hybrid, it you would not be able to use your physical games, and possibly digital too depending on how greedy Sony gets with it.

The PS4 is disc based, which is harder to put into portable format due to scratching disks and moving parts. They would have to Switch to carts or go digital only. I do not think Sony is going to explore this avenue. I believe they are going to keep plating the power race with MS and leave the Hybrid concept to Nintendo.

ps4 level power and affordable? i would say 5 years

Xavier's TDP is in the 20-30W range, way too high for a hybrid console, which can stomach only up to 5W (give or take) without getting too hot or draining power too fast. Also, most of it's power comes from the Tensor cores, but Videogames don't make use of them (hence why Volta is a pure HPC card with no consumer models).

With some custom design, you can however probably reach about XBO power right now with a 14-10nm chip without consuming too much. But since such one would need to get designed first, it would still take about 2-3 years until it's release.

In 7nm, a PS4-level APU with about 5W TDP is possibly feasible if one looks what Raven Ridge can pull at 15W TDP, but I wouldn't bet on any earlier than this for a technological feasibility of a PS4 hybrid for less then 500$

Uh, no. It's not that simple. Cooling efforts needed for such power woud prevent it. Five years - maybe.

The APU in the PS4 is already tiny. It will easily be possible, maybe even already with the next shrink. Though it might not be possible with an AMD APU any time soon, but rather an ARM SOC.

Around PS4 level of power hybrid will probably be posible around 5 years for $300-400. But PS4 level power is not same thing like PS4 hybrid.

3rd party devs had huge problems with PS3 hardware 1st few years but later they utilise PS3 hardware much more. Also 1st party games on Switch will also use most of Switch hardware, most of PS3 1st party games are linear 720p/30fps games, while for instance MK8D is 1080p/60FPS game, ARMS is 1080p/60FPS game, Mario Odyssey is 900p/60FPS game, Zelda BotW 900p/30fps...and we talking only about 1st year Switch games, offcourse that later games will use more from Switch hardware. Thats why multiplatform games show quite difference in favour of Switch, when 720p PS3 game runing at 1080p on Switch for instance we talking about huge difrence in power, aside in most cases better visuals and more stable frame rate.

No it's not tiny, PS4 draws around TDP of 80W, so they would need to have TDP thats around 15W. But thats a problem, if you use ARM instead of AMD CPU thats in PS4 APU, PS4 games wont work on sucha device. There is reason why PS4 Pro and Xbox X used same CPUs that in base PS4 and in Xbox S, in other words, PS4 Hybrid need identical hardware that's in base PS4 and that's actually biggest problem for possible PS4 hybrid.

Yeah, that level power, I agree, probably 5 years. Full PS4-compatibility? I dunno, I agree with Miyamotoo, that shrinking the ship never will happen. So in 10-15 years emulation, that might be possible.

Yeah, I agree Switch is more powerful. Only saying, the difference might look bigger in multiplat comparisons, because some potential was untapped in PS3. But no way this much.

NOT irrelevant, because ps4 has GCN cores doesnt mean it can only run on GCN architecture, never in my 2 years of coding on PS4 had anybody told me and my team to stick to basic GCN architecture we havent even touched it, GCN is one of the option for people who wanna port their games with ease.. but writing own instruction set and frame work is far more rewarding and completely dwarf what we are able to achieve on PC with similar kind of hardware, the only complaint we have is that, of CPU grunt to save some frame budget. 

AGAIN Just in lay man term what a custom architecture can do is you have to look at PSvita with off the shelf SoC compared that to similar or more powerful hardware. Now I m not saying PS4 level of graphics is possible the difference will be similar to what PS3 and Psvita had. Which in my opinion will be far better than what switch is delivering right now.

What are people talking about here?

x86 and full compatibility? Won't happen to soon.

ARM with a comparably strong GPU? Might be not that far away.

PS4 power in docked mode? Again, that should be available in a not so far away future.

PS4 power while in mobile mode? There is a reason, actually multiple reasons, Switch clocks down. The same would apply for every other handheld.
Battery life, not only in terms of how long one charge lasts but the overall lifetime.
Cooling/getting rid of the heat. Switch actually has a built in fan. But the more power, the hotter it get's.
Cost. We are talking about SoC, RAM, FLASH-memory...

Yes, there are those nice things like die-shrinks. But a new node isn't always what it seems to be. Companies started 'cheating' about transistor- and gate sizes and other stuff some time ago. Two different 14nm manufacturing processes might be incomparable today. And new manufacturing steps don't always bring the expected results in cutting costs and improving energy efficiency.
Finally, new shrinks take longer and longer the closer we get to the limits. Not to talk about stuff like bus width and other 'little details'.

Tegra Xavier right now is intended for AI systems, deep learning, self driving cars and stuff like that. Mainly because you make more money there than with a gaming device or tablet and Xavier is relatively expensive in the beginning.

A Xavier device should come relatively close to PS4 power levels, at least in docked mode and would be possible to built very soon. But not at the 400,-$/€ pricepoint.