I think it mostly died out. Or was replaced by X11 servers (depending on your definition of a graphics "terminal")
DEC to my knowledge is the company that had them.
Who knows what crazy patents might have been in effect during the 80's...
However, there is another standard called Tektronix (in theory can be run with xterm with the '-t' flag segfaults on my copy in Linux Mint)
I believe this standard is for oscilloscopes but I'm not 100% sure.
I think X server kind of killed vector graphics terminals.
It would be really cool to just render graphics without needing a library or worrying about "here today gone tomorrow" libraries. (Anyone attempt to get old Motif programs working?
Once you have a hardware graphics specification for a terminal the rules are sort of set in stone. Which is why we still have the vt100/102 standard for terminals today.
I think a good solution now is a software layer that can take output , parse it to screen displays, and return input from the terminal.
In this way, we can write timeless GUI software while only worrying about writing a software layer to handle the program output.
Programs from the 70's still run OK today in most cases with our modern terminals. Pair that with graphics and you have timeless graphical programs.
Granted these graphics are primitive, but pixels themselves are the building blocks for our most advanced games and simulations.
Take a look there, that must have been mind blowing for the time. This program could probably run today if compiled and hooked to a terminal emulator.http://modularsynthesis.com/tek/
Just a thought.
We could even define a new standard.