The question is "who's left," not "who's actively getting off their fucking lazy ass and doing shit," Grae.
Hive mind detected. But pretty much this. People seem to have largely discovered the joys of RPing in their own environments on their own (or friendly) terms, instead of engaging in the Tumblr-esque parade of artificial outrage and line blurring that public Rp can become. Not to say public RP doesn't have it's place, but I'm certainly enjoying kicking back on my terms instead of throwing snippets into the wind elsewhere.
So who is left in RP? Everyone who is. What does it matter so long as you can meet one or two like minds?
In the OP, the question was raised by a vet returning after a two-year absense, but the fact that active players are still asking the question six months later indicates to me that there's little reassurance at present that one can meet those like minds outside of 'public RP' (along with the associated complications which it can inspire). One could roll alts until they had a concept that matched well with an existing clique, and try to insinuate one's self into the drama, but that would limit one's effectiveness in actual gameplay. Clone Grade Alpha is not conducive to W-space superiority, for example.
I'm thankful that there is at least an OOC channel for chatting up RP enthusiasts, as most of the small-time lowsec operators I used to have contact with have left the game. While there's no character development, it's still more entertaining than the client itself or writing mediocre fanfiction.