I've got a couple suggested modifications to add to what sd-7 listed for this:
In the years since then, the number of these partakers has progressively decreased, principally because faithful Witnesses of Jehovah finished their earthly life course in death.
How about one of these:
In the years since then, the number of these partakers has progressively decreased, then progressively increased, principally because the faithful anointed have finished their earthly course and the Christian congregation has recently experienced a significant influx of mentally unstable individuals.
As the Last Days wind down to their finish, we can expect that the number of partakers will progressively decrease. Since Jehovah has chosen to pour out his Holy Spirit to anoint an ever increasing Little Flock to numbers not seen since the 1960s, it is reasonable to conclude that the end is now further away than what some Jehovah's Witnesses had led themselves to believe. Are we not indeed happified to now realize our privilege to preach the Good News of the Governing Body could easily extend for another 50 or 60 years? Think of the dozens of lives that might be saved during the final overlapping decades of this never again to be repeated work!