The term died, the dream festered on. It got rebranded as model driven development andany in the embedded world bought into it in the late 90s, some have only ditched it in the last year or two, while plenty more have followed a second rebranding and keep drawing... There are some good graphical languages, lego mind storm, code spells, gnu radio companion, simulink, and maybe, sometimes, labview. Those languages aren't object oriented, they represent data flow. I suspect that makes a difference. But mostly they are for quick prototyping or small designs. And that makes an even bigger one. Diagrams don't scale well.
The first 3 generation of languages were powered by higher levels of abstraction, which were possible because of better machines.
However, further increase in level of abstraction did not make developers an order of magnitude more productive, except for niche areas. Switching to a better development process (Scrum) can achieve order of magnitude improvement in developer performance, while switching of programming language cannot.
Anybody can claim that their product is a next gen revolutionary market shaking breakthrough. It's the self-promotion, not a science.
https://en.wikipedia.org/wiki/Fourth-generation_programming_...
They considered things like excel 4GL: You program some formulas and excel magically finds out what the necesarry steps are to do the computation.
A lot of vendors created graphical programming languages and declared them 4GL. The term mostly died because nobody could stop laughing.