> Given the power and ubiquity of smart phones, most people don't need any other computer in their personal life.
Maybe, but they need other form factors, too. Like a big screen and a keyboard.
And once you have those, you might as well through some compute in there: getting smartphone-like performance out of desktop-like components (or even laptop components) is pretty cheap, so might as well throw them in.
Chromebooks are fairly capable 'thin' clients. Their specs aren't that much worse than other laptops.
However all that being said, I mostly agree that at least with current style AI we will likely see a lot more data centre compute in the future. At least as long as hardware costs are a significant fraction of total costs: the 'cloud' can multiplex multiple users over expensive hardware, your local computer is mostly idle and waiting for your input. (And it has to be, if you want low latency.)
However, if costs shift so that electricity and not hardware is the main cost, we might see a return to local compute. Maybe.