We have to be careful with this because it's illogical for a programming language to really become "irrelevant" if you think about it hard enough. The reason why is because most of these languages are all Turing Complete which, in this context, means that each one can do anything any other can. Therefore, it's sort of like asking "which raft color is less popular at the raft store?"
The raft color question is a valid question because in reality, perhaps blue rafts sell way more quantities than gold rafts... However, every single raft will perform the exact same way at keeping you afloat on the water, regardless of its color. So while a green raft could become, as you say, "irrelevant," is that even really true? It depends on what you're looking at. I look at a raft's ability to keep me afloat in which case the green raft, even if it sells 0 ever, is still relevant in my eyes.
This is how I view programming languages. Languages which are good for some given task aren't so mostly due to the constructs of the actual language, but rather, the cultural following behind each language. I.E. "What was the purpose the language author conceived the language for?" and "Which community has taken to the language the most resulting in the most libraries?"
Another thing too is, many would consider assembly language to be "irrelevant" today because I don't know a single person who really programs in it for anything major... But it's not at all, for without it, you would not be able to effectively analyze binaries and find vulnerabilities and such, since it is an explanation of machine code essentially. Would you say now that we have marble flooring and beautiful chandeliers, that the ugly, boring, concrete foundation is irrelevant??