After witnessing many of these discussions, it's just FUD. Just because Emacs is older doesn't mean that IntelliJ or Eclipse aren't likely to follow you until retirement. Java hit critical mass a long time ago and both IDEs have mass adoption and are also OSS, as you mentioned.
The POV presented in that comment is basically a sales pitch. It's too standardized and common not to be (it pops up in most of these threads).
There is an interesting rule from biological evolution of rates of extinction with species age that I'd thought of in relation to this. Essentially: they're constant. That is, a species is as likely ro go extinct when old as young: there is no increased survival probability with age.
Leigh Van Valen's Law of Extinction, related to the Red Queen Hypothesis.
The POV presented in that comment is basically a sales pitch. It's too standardized and common not to be (it pops up in most of these threads).