I don't think Sanc can be used as any measure of how many "old guard" have stayed in the game. I don't believe any of my Org, who're all pretty much Alpha players, some with a couple or three "backer" accounts have placed STUs on Sanc Moon. The problems with issuing STUs mean that Sanctuary tiles have no distinct reason for grabbing and are only being claimed by a few old timers who like the place specifically, or are doing it "because they can", or any other personal reason.
In similar vein, I don't think any of my org-mates are using actual money to play the game; that's all been paid up-front, years ago. Might be a couple of "discount annual sub" alts in there, but mostly running on DACs they bought with packages.
I have never seen a player from another Org. I've seen their ships and statics, but never actually managed to bump into one in person. I don't go to the busy markets, but back in beta, there were always bods around-and-about on Madis. Either the necessity of leaving your hutch has reduced, or the numbers are well down on that period.