I think it's even more interesting than that - I find our current 'solution', that being all manner of 'chassis' that we put mostly standardized parts into - to be fairly inelegant and necessary largely due to a lack of collective will to standardize.
I'm sitting here next to a Lian Li O11 Dynamic XL, which houses my personal desktop. It's the largest desktop case I've owned in the thirty years I've been building them, and I went with it for one reason only: to have more room to work inside the case.
As I've been able to pick up a 3080 and have started venturing down the Alder Lake path, the larger Lian Li case has proven to be a great companion.
Thing is, if you don't need to work in a system, and you don't need the highest-TDP parts, well, you could get away with an SFF the size of a toaster!
Now, to the meat.
With the proliferation of fast network interconnects as well as a wide variety of virtualization advancements, I can see 'desktop computing' going a similar direction that 'mobile computing' has already gone, that is, punted off to some big iron on the other end of a network link. Everything from 400Gbps fiber to variable-frequency wireless links can bring latency down to manageable levels with the 'local machine' being used primarily for the user interface and feedback-intensive work.
And if you consider what is within the realm of possibility today in say a <100W package, something that can be reasonably inconspicuous in terms of visual and aural footprints (small and quiet), I'm thinking that we can get pretty far toward 'computers' really being tuned for whatever I/O they need to service in terms of user interaction. Like phones, you really wouldn't need to upgrade them very often, and they'd really be more like appliances with decade-long or longer service lives being a given, like laundry, refrigeration, televisions before the digital age and now into the 4k age, and so on.
Very likely few will actually 'need' significant local compute resources. Gaming is literally the main consumer workload that has fairly absolute interactive latency limits, so it's likely to remain a bit of a special case.
For any other 'heavy' processing, whatever that might be, it can either be done on a local compute node (in a closet, etc.) or farmed out to a cloud environment of some sort.