Nintendo pulled Switch off, because they had multiple things going for them:
a) Nintendo is going all in with game production with Switch being the only system they have in the future (3DS is supported as outgoing system). This was possible because WiiU was a dud and 3DS is at end of life. If Sony does something like that, they had to wait until end-of-life for PS4 and they are risking all on it, while a normal PS5 would probably similarly successful.
b) Switch was a step-up in power, because WiiU was comparatively weak and it was possible with mobile specs to outdo this. I don't see any mobile system with acceptable price could outdo PS4 (or even more: Pro). So if Sony does that, the system would be weaker, which would take away from the perceived value. People would stay with the PS4, because it has an established library and is more powerful.
c) Switch is less powerful than Xbox One and PS4, but close enough that it doesn't matter in eyes of many gamers. Look at Skyrim and Doom for examples, that the games are possible and the graphical downgrades are acceptable tradeoffs for portability. This was only possible because of the mid-gen release. Earlier this wasn't possible for the price and some time later people would expect a step up in power expecting the next generation. But as PS5 and nextbox are still far away most people don't compare with their expectations for next gen. If Sony does a hybrid as replacement of PS4, then people would expect a generational step in power.
d) As WiiU was a dud and 3DS nearing end of life, the risk to compete with own machines was small. If Sony concentrated on a hybrid alone it would be a tremendous risk. If they magically would produce a hybrid that magically can play PS4-games at the same power it would make the PS4 obsolete. But that seems technically impossible. Mostly because a mobile console wouldn't be able to work with optical discs and probably with other chips. If they make a console that is similar in power but incompatible to PS4 games, the two devices would compete and eat into each others market. If they make it only portable, the markets would no longer overlap, but it loses the desirability the Switch has.
3DS-FC: 4511-1768-7903 (Mii-Name: Mnementh), Nintendo-Network-ID: Mnementh, Switch: SW-7706-3819-9381 (Mnementh)
my greatest games: 2017, 2018, 2019, 2020, 2021, 2022, 2023
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