Cool concept.
The likelihood of it happening is low, but there's a lot of really great opportunities here especially with the new wave or ARM PCs coming. I don't know what the device form factor looks like, but I wouldn't mind carrying around a pocket PC - a true mobile computer. Already with the Windows Store, you have access to tons of apps. For the apps that aren't in the Store, there's the browser. That seemed to be good enough for Apple's Vision Pro. Taking it a step further would the app gap matter as much if you have Copilot as your concierge orchestrating tasks for you using the various services? Better yet, what if these services had their own assistants / GPTs Copilot could talk to and coordinate on your behalf?
At some point, I might just use OpenAI's Sora model to live vicariously through an AI-generated video depicting this alternate reality where Windows Phone exists...