Well, it's always been that many of the young generation strikes out on their own for a bit. Many of those return to the WTBTS though, due to the massive amount of guilt that was instilled in them from an early age. The recent trends have been, and this is all anecdotal(sp?) , that more and more of the young generation either leaves entirely or lead 'double lives' - proving they are not buying into the WTBTS message of gloom and doom. This is especially true in 'western' lands where things are pretty good, and information flows freely.
As to the WTBTS increasing, that is due in a large part to countries where the general population is in poverty, or poor living conditions. Lands like Africa and Brazil are booming for the JWs. The message of a paradise is appealing, and the religion is young there. People are not tired of the years and years of empty promises like they are in lands where the JWs have been strong for a long time.
As to it collapsing, I doubt it. I think it will continue to decline, but there are a LOT of people in it who have the mental capacity that if they walked in on a Governing Body group orgy they would dismiss it without a second though "Oh they're just imperfect men". Those are your hardcore JWs. Nothing phases them.
One other item to consider is the real area of interest to the WTBTS, money. It's drying up. The countries that are growing are poor ones, and cannot send the $$$ that the WTBTS are used to. And in lands like the US the JWs are in such a state of apathy, the $$$ are WAY down. And trust me, THAT's got the old men more worried than avg hours in FS, # of pubs, or mags printed!