I have been following this phantasy for a long time (starting with the Atrix lapdock, continuing with the Nexus 4 running Ubuntu Touch and a SlimPort dongle, Nexus 5 and MaruOS and ...
Now I have a PinePhone and even made a few videos for YouTube (PeerTube, LBRY) demoing Phosh (the Phone Shell developed by Purism), Plasma Mobile and also Plasma Desktop and Gnome (the Mobile Shells have improved since, as they are still in early development). Honestly, Gnome and Plasma Desktop felt way better than their mobile counterparts. I think that this is not just familiarity, but also that they are made for the use case primarily.
It turns out that the UX affordances are sufficiently different between a small touchscreen and keyboard/mouse/monitor that the software has to look completely different. Attempting to get it to automatically adapt (Metro) is an even bigger stretch than responsive web design.
While it's quite possible that Apple will eventually release an iOS desktop, I don't think using the same device for both will ever work properly.
This is what the cloud is for. You're now going to tell me that you don't like that and would prefer local-only storage, but it seems like the vast majority of home and corporate users prefer otherwise.
> Use the same cpu/ram/gpu for both.
.. attached to your display and keyboard by a single USB-C connector. Or I suppose Miracast.
This turns into "would you like to buy a surprisingly not-cheap dock that's useless without the phone, or a separate computer that's properly adapted for its use case". Like 3D movies, it's something that the industry periodically comes up with, pushes for a while, and nobody actually wants because the compromises are too much of a downside.
It's far more likely that "smart home" and "smart TV" stuff will, very slowly, converge into a single integrated ecosystem where you can easily use your phone to control Netflix on the TV. "Casting" (a la chromecast) shows the way forwards.
Also, quite a few people say they need 32/64 Gb of RAM, multiple high resolution monitors, large disks, huge graphics cards, etc. I don’t see a phone-sized device ever driving that, as needs will grow with hardware speed ups.
As for the 'there is no money in that' argument I believe that there is plenty of money in various iDOCKS, accessories, doodads and similar.
Because of that, I don't buy this particular theory - the first of the big players that provides a workable and friction free product will surely have it worth their while.
Also, for that predominant customer houses the device for consuming entertainment, I would think Apple TV + HomePod is more friction-free than a desktop could be.
Televisions have larger screens and are placed in better locations inside the house for that role.
Now the software... I feel like it's being redone for the fourth time.
I haven't used this, but it seems similar to what you're asking about