So, basically we are going back to the single (all functions) mainframe with offsite (dumb) terminals. Like the obsolete systems we just rid ourselves of. Yay, no more personal storage, trust big brother.
Although they won't be "dumb" terminals, they'll simply boot to whatever Service Provider we choose to subscribe to and run our OS of choice remotely, presenting us with the UI (User Interface) that we choose. There will still be a form of boot level kernel in the endpoint that you use to connect to a service and that kernel will be configurable by the end user to point to whatever service they choose.
I can do that today with a beta device I have @ home that points to a service, boots up a virtual instance of Ubuntu 20.10 or Windows 10 (which ever I prefer) and gives me the UI for the OS I've chosen.
My home connection is WiFi6 to my home router, which is plugged into a Motorola Cable Modem that's capable of up to 1GB up/down speed to Comcast.
I pay for a 300mb/down, 30mb/up connection to Comcast. Using my beta device, I can boot to either Ubuntu or Windows 10 today from home in about 30 seconds. Want it to go faster? Get a bigger/faster pipe or simply skinny down the requirements of the OS. For giggles I run a pretty loaded up Ubuntu 20.10 instance so it takes a bit to fully boot up and connect to my beta device. Simply disabling services on Ubuntu speeds that up pretty dramatically.
Windows 10 boots up in about 22-23 seconds and it's pretty loaded up also.
Microsoft is already saying they'll have Cloud PC's in 2021. It'll be interesting to see what their definition of "Cloud PC" really is.