But for a broader definition of "personal computer", the number of computers we have has only continued to skyrocket - phones, watches, cars, TVs, smart speakers, toaster ovens, kids' toys...

I'm with GP - I imagine a future when capable AI models become small and cheap enough to run locally in all kinds of contexts.

https://notes.npilk.com/ten-thousand-agents

Depending on how you are defining AI models, they already do. Think of the $15 security camera that can detect people and objects. That is AI model driven. LLM's are another story, but smaller, less effective ones can and do already run at the edge.