As long as there is a growth in numbers shown (by manipulation of those numbers) I don't think there will be any tipping point.
I remember the exodus of 76-79 and a few apostasy leavers in '81 - I was a mid teen and a lot of my peers left or didn't get baptised but around my then congo the numbers stayed steady afterwards. The numbers at our hall in the late 70's are little different than they are now - helped by higher than average longevity, especially in women and "low quality" mentally or emotionally challenged converts.
We still have a steady turnover, a few die-hards, with numbers staying about the same.
And in my extended family on both sides of my marriage I would say that many of the 17-35 age group have stuck with it, sadly. And that in some form of fulltime service (tm) or MS/Elder unless they have left to have kids. Even those that have got disfellowshipped have "gone back".
This group study change has made quite a difference - less pressure - and I think that slowly this religion will dumb down and require less effort (beyond blind obedience in lip service and money giving) - in our hall two meetings a week and once in the min each week with a bit of padded "incidental witnessing" (tm) and a report of 7/8 hrs = min.serv! Four hours will keep you in "good standing" and let you run a microphone.