Several people on here have said it before - the glory years of the WTS were the late 1950's to 1975. They were having massive conventions, they were recruiting 'normal' young people who were on a post-war high, and they had a specific date for the end of the world.
1975 punctured the tyre
1995 completely deflated it and running flat from 'our' perspective - as far as we are concerned the Borg is not attractive. Other people see it differently.
See the 20 year picture? This organisation is not going to blow up anytime soon, unless they self-destruct somehow
My prediction:
2015 - move out of Brooklyn complete. Healthy cash balance and operating costs properly aligned with decreased income.
2035 - fully adjusted to the new operating cashflow model they are 15 million strong (3% net growth per annum will get them there in that time scale) with English nowhere near the predominant native language. Low operating costs combined with small but numerous contributions from the 3rd World will keep the GB and HQ leadership in lifetime comfort, if not in style. (The newly appointed GB member born in 1985 has not yet attended the MTS and is currently 25 years old) The Nigerian villagers speak in awed tones of Ramapo and Kerplunkadunk.
Check back later to see if I was anywhere near the money :-)))
EDIT - I agree with Metatron - a black swan event could take 'em down at unparalleled speed