One of the most persistent myths on this website is that JWs are already in decline, the rot has set in, and the descent of the Watchtower is inevitable from here on in.
That isn't really what people have said. At least I certainly haven't. What has been said is that the rate of growth has declined. And that is indeed the case. It is also the case that in many countries, the rate of growth is lower than population growth, which results in a relative decline.
And the countries that are seeing the most growth tend to be those that are less sustainable because the people in those countries have less money to give.