I scraped a representative set of Slashdot comments a few years ago and it was notable that only the users in the 100K to 300K UID block were very active with a progressive decline over the years. AC posts picked up as mobile became more common but that wasn't enough to compensate for the loss of logged in comments. Projecting forward, it was clear that the core commenters would age out completely by 2022-ish. That is when I expect Slashdot to go belly up.