There’s a difference between lower baptism numbers (true) and decline in membership (not happened yet).
As said by others, there are several factors that create vagueness about who is a Jehovah's Witness or not. So for me, I focus on the number of baptized people, where, according to anecdotes, the majority are children of Jehovah's Witness parents. I have already made a graph, comparing the baptism curve with the curve of the publishers and it is clear that the number of baptisms does not follow the publishers, suggesting a strong shrinkage. But you don't even need numbers. You can see that when Jehovah's Witnesses are preaching, no one cares about them, no one stops to listen to them. And I'm saying in Latin America. In the US and the EU, things could be worse. Also, when I mean decline, I mean the number of empty seats in KH. In my city, KH have been sold for a long time and congregations are reagrouped as single one. So if JWs aren't in decline, I don't know what name could be used.