I've been using pretty much the same features from org-mode now that I used when I first started using it at least 11 years ago (actually, probably using even fewer features now, in the beginning I would export things, but these days I rarely see the need). All my notes still work, and are still plain text, and still don't rely on any "ecosystem", just Emacs and git.

Emacs and org-mode will still be here (along with the armoured cockroaches) long after we're all gone. In fact, I have more faith in the longevity of emacs than I do of Android or iOS, or Evernote/OneNote for that matter.

well, without any extra information, the expected future lifetime of a thing is proportional (equal, actually) to its lifetime so far. therefore, yes, it's perfectly sensible to expect Emacs to last longer :)