Factually wrong.

Huh? The Switch is a hybrid device, and when docked it uses like 20-25watts too.
At those power ranges today (15-25w), AMD actually does have a chip that can do ~1.66 Tflops (not quite 1.84) but close.

At docked *handheld mode it would like the switch, need to run games at lower resolutions (and thus use less power).

10nm isnt far away, a shrink of a 2700U chip, for amd could probably make a "switch" version of a PS4 possible today.

Depends on how much money you wanna lose

5 years at least and it still would very expensive.

The performance gain is more than linear when the node shrinks. On TDP parity you have 2 kind of gains. You can fit more transistors in the same area and since operating temperatures are lower you can increase clock speed. Maybe I'm a bit too optimistic but I think a performance between the OG XB1 and OG PS4 (28nm designs) could be potentially achieved on a 7nm chip. 

I wouldn't pay much attention to what AMD is claiming - go to GFX Bench and look up 2700u vs 7850 (which is around PS4's performance) - it's more than 2x slower.

AMD will get there eventually, but not just yet - and they need to have SoC that is capable of running PS4 games as they are, not with lower res/settings like with Switch where games are made from the start for both modes.

All games need to be installed for a 5400rpm harddrive and the ps4 uses GDDR5 memory not to mention the jaquar cores will never be in a portable ps4 so they would need to use a new cpu technology like ryzen and put in the effort to make it all compatible, seems like a significant effort.

This post is so wrong. Switch is more powerful than Wii U which was already a bit more powerful than PS3/360. Switch is not only a good deal more powerful but uses modern architecture even more modern than PS4. 3DS is inbetweenPS2 and Gamecube but more modern shaders.  GBA was more powerful than SNES and why there was a good amount of 3D games on the system. Game Gear was mower powerful than Game Boy and was essentially a portable SMS. Game Boy Color did not have the same power.  As for the OP. A few years. Xavier is a few years off being ready for a portable system for power consumption heat and battery life. By the time Switch 2 launches in maybe 2022-3

But would that be compatible with the ps4 library? 

Dedicated handheld gaming yes. And I was proven right. Neither Sony or Nintendo are showing any signs of releasing a traditional dedicated handheld anymore. 

So the chances of getting a ps4 portable that plays all ps4 games is pretty much zero. 

There are games on PS3 graphically and technically more impressive then switch games so I don't see how you can say its above it.