If I understand well, the ESR version will be maintained with security updates one year from now.
If one year is "very near future", I guess you are right...
I don't know if anyone answered this before, but I just found an easy solution that works for me (on Windows though, but I guess it would work on Linux as well.
Just download and install Firefox ESR here: Mozilla Firefox Web Browser — Download Firefox Extended Support Release in your language
I...