How long until Cloud Computing and internet speeds develop to the point that someone could pay a monthly fee to access a full OS and superior processing power from a server, rather than from an expensively designed box. iCloud and Dropbox are the infants of this technology. You could potentially sign into your computer from any piece of glass you have to hand, without necessarily being tied to a specific brand.
That trope has been around since the 1960s, maybe 1950s. I've heard that exact same story back when I worked with others in the 1990s when "100 megabit Ethernet was it! This is gonna do it! We have the bandwidth now! 10x what we had with 10mb!"
Uh-huh. Didn't happen. Oh we had fake versions of it. One was called "Citrix metaframe". Yeah. That Citrix. Same crap as today. Except the server backend kept changing. SNA and a token ring bridge (serial lines to dumb TN3270 or TN5250 terminals), no now it's OS/2, no now it's UNIX (of various varieties) with remote X display terminals (ahh good ol X11 hack days), no now it's Windows (ugh a mess with 3rd party crap), no it's UNIX again or rather Linux (back to X displays and Hummingbird client for
Windows), no the other UNIX (Solaris, or AIX maybe), no back to Windows with straight Terminal Services, but the cheap one.... ok we'll just do all of them (Citrix Winframe.. geez a disaster). Now it's a virtual-ish thing ... oh crap now Microsoft did one themselves...
At times, the fad was Terminal Services, then the TS gateway blah blah, then Remote Desktop, then RD Gateway, no now we gotta do all the varieties...
Then other random small time hack job players like SecureLink...
All of these are terrible, all of them fail to do the job... "thin client" is a mirage because YOU CAN'T DO THIS!! You'll never have the bandwidth, you'll never have the "right" backend, it's easier to push the work to the client and the server transmits small data and let the client do more of the work (iCloud).
Having a pool of big honkin' servers with humans and expertise is expensive and no one wants to put that much money, time, and work into it. Now Microsoft does the Windows 365 subscription which is.... RD Gateway effectively but massively distributed on their infrastructure that you pay them to be the specialized experts (which they are, and spectacularly so; kudos to them). Even so, that requires some "recent version of a client for Remote Desktop on some recent PC or device.. none of which are super thin clients.
So no... no such thing as "super thin client" that will be universally operable. People tend to want their work/data/"files" on hand when the Internet goes out. Unplug your cable modem and count how long before your family of "users" comes screaming. I wager 5 seconds... and don't say "well you can have a local cache with some viewer app in read only mode..." bzzzt. That's by definition no longer a "super thin client".
This is a pipe dream. And pipes are meant for smoking.