The WTS has always reinvented itself.
In 1908 a group of Bible Students left and the WTS survived.
In 1918, the WTS board of directors were imprisoned but the WTS survived.
In 1925, after Rutherford's prophecy that the end would come then, that the ancient worthies would be resurrected to rule on earth (Abraham, David, etc.) failed and 3/4 of the membership left, the WTS survived.
In 1975, after the prophecy connecting the end to that date failed, there was a decrease of 2% for the years of 1978 and 1979, the WTS still survived.
Those alive in each of those periods eventually die off and what is left is people who were too young to understand and new people who came in afterwards. The WTS bets on this. When the boomer generation of jws dies and the new doctrines that shape the remainder's view of the end take root, the WTS will still survive.