Of course there is, switch is enormously successful and it's a handheld. You can pretend it's a console but if you take away it's portability it sells 10 million vs 100 million. 3DS and DS numbers aren't relevant to today's market.
It is not "just' a handheld. It is a hybrid console, and that distinction is important to make because a hypothetical Playstation Handheld , even if it was a hybrid console, is primarily going to have to appeal as a handheld device for reasons I will explain in just a bit.
What? What do you mean being a hybrid doesn't have value? It's literally one of the biggest reasons switch did so well out of the gate, the idea that you were getting a console and a handheld. (and still does)
Your going to sit there an pretend that a Sony handheld wouldn't have any extra value if it easily hooked to a TV? So nobody wants their console to be easily moved? Or used on a secondary TV?
To say nothing of the people on the street that care more about playing sony games than getting the best graphics? Perhaps they would like a console that they can play on the TV sometimes. To say it has no value is ridiculous.
Making it a hybrid is not going to increase its appeal for a variety of reasons, and I'll explain why this is different for the Switch.
The Switch's hybrid nature is indeed part of its success. You're getting a home console and a handheld system for the price of one. But this also means that different audiences are rolled into one product. No matter if you want to play your Nintendo games on your TV, Handheld or a combination of the two: You have to get a Nintendo Switch. Nintendo is currently not supporting any other products besides the Switch.
Here is where that differs from a hypothetical PSP2: The Playstation 5 exists. A large portion of your potential audience is going to be Playstation fans who, more likely than not, already own a Playstation 5. If you already own the Playstation 5, then the hybrid nature doesn't benefit you at all. Even if you could hook up your PSP2 to a TV, why would you do that if you can just play those games on a much more powerful Playstation 5 instead?
So the only benefit you have is being able to play the games you already have access to on the go, and asking people to spend another 300$ ~ 500$ to do just that is a really hard sell. Especially since you're now also entering a market that is dominated by Nintendo: Just because the Switch is successful, doesn't mean a hybrid PSP2 would be too.
Yes, talking about PS5 games, and yes, easily ported to a handheld with very similar architecture and scaled down to a lower resolution. No different than Series S from Series X.
As to Sony not having developers, it's no different than xbox and series S, it wouldn't stop anyone from making PS5 games. The game is different now, the reason Nintendo went away from 2 systems was when they had drastically different architecture and yes, it would split the user base.
Sorry, but that's just not how any of this works. Your argument seems to be based on the misconception that "similar architecture" is some kind of secret sauce. You can't just cram the hardware specs of a system similar to the Series S into a handheld device. It would require a giant device and the battery would only last for an hour, not to mention the exorbitant price of the system. This is neither feasible nor realistic.
If a PSP2 is going to happen, it's most likely going to be a cloud/streaming device, as it would be much cheaper to produce.