The fact that this current generation does not want to make unnecessary sacrifice may very well be the final nail in the coffin. Here are two of the biggest factors effecting the organization in the U.S. -
1) Nobody really believes the end is near. Overlapping Generations is the 1975 of the late 20th century/early 21st century. In fact, it is much worse than 1975. This doctrine basically means that the end may never come in this century either.
2) Generation Y or "Millennials" have a much different value system than Generation X and Baby Boomers. Generation Y seeks balance between work and play. Jehovah's Witnesses teach that one should sacrifice satisfying all desires of today for a future that may never come in your lifetime. That is in direct contrast of value system in the new generation.
There will always be those uber-dubs that will qualify to be Ministerial Servants and Elders, but the organization is losing them at a higher rate than appointing them.