Random thoughts on this interesting topic:
It would be helpful in this discussion to establish some criteria that remains consistent, such as a definition of "decline." By my definition they are in decline - we won't see a complete implosion, but I think we are beginning to see a "hollowing out" - most of those in are going through the motions, the 'fire in the belly' isn't even embers anymore.
There is a wide variance on the continuum between "modest growth" and "last one out the door, turn the lights out."
I doubt that we will see in our lifetime a scenario where the GB says, in effect, "The jig is up! We've been stringing y'all along all this time."
When they abandoned 1914, they lost the lynchpin that ignited a sense of urgency. Without urgency, people become lackadaisical, dull and easily distracted.
Once a JW reaches a certain age - say 60/70 - they have more reason to stay in than to leave, even if they suspect TTATT.
Can we trust their numbers? They've changed their definitions of "pioneer," "publisher," "generation," etc., perhaps they've changed the definition of who they count as a JW.
I once calculated that, of my large JW extended 3rd and 4th generation born-in family, at least 60% had left the organization.