I don't have an encyclopedic memory. I just got in the habit of scrolling through all the Latest pages on imgflip when I was trying to keep track of the Kermit vs Connery memes.
I'm not sure exactly what kind of answer you're looking for (e.g. what measuring standard you would use) but personally, I haven't seen anything to indicate that there's any kind of generational change / praetorian guard switch-out. I think that's just a case of people trying to make patterns out of things, and perhaps the natural human tendency to think "our time" is the most important time. There are always people leaving and always new people coming, just like on any site. To be honest, I haven't even seen that many people leaving. At least, not any more users seem to be leaving than any other time while I've been on the site.
However, what I have noticed is that in the past several months or so there has been a noticeable increase of new users being added, and the amount of activity on the site overall.
But who knows? I see a lot of stuff on the site (more than an average user does, maybe), but I don't see everything.