That has been my impression of present dynamics and historical data, too - boom-bust-cycles of either some other platform fucking up or there being curiosity from some synergetic effect, then the initial wave breaking over time - but usually also leaving behind at least more (genuinely active) users than before the wave. For Lemmy, one can definitely see some reduction in activity, I think - not dramatically, but I do think it’s noticeable if you spend a lot of time here. E.g. unlike during the last Exodus, I see more of “the same users” than before. There’s still enough content, it does not feel dead by a long shot, and who knows when the next wave may hit.

That wave-like character makes it hard to estimate organic growth too, at times. The mass influx of users dying off over weeks will give shrinking numbers there, even if some users from organic growth who are more likely to stay and be active than “mass exodus users” may still join there. Also, users moving in between MBin/PieFed/Lemmy will fudge numbers, but they are essentially in the same ecosystem.