The main question is, What is a generation?
A "generation" is a cohort of people who were born in the same date range, end of story. My generation is not the same as my parents' generation nor of the 'younger' generation that say, are in high school right now. It is your contemporaries-----those that are similar in age to you. As even the Borg has confirmed thousands of times in the pages of their literture, a biblical generation is 70 or 80 years.
By the bizarre logic that they are trying to use to weasle their way out of an obvious false doctrine of theirs, they have come up with a completely crazy theory; that Jesus was "evidently" talking about an "overlapping generation"----an idea that appears nowhere in the bible and is based on absolutely nothing.
My grandmother was born in 1891 (she was in her mid 40s when she had my dad) and she died over 35 years ago. I was very young when she died, but I remember her. Now lets say I live for another 40 years which would bring us to the year 2050. By the WTS's "logic", a "generation" could now mean 160 years if you "overlap" it. That, of course, makes absolutely no sense whatsoever and there is nothing to back up such a ridiculous theory. There is a reason it's referred to as "this generation". Jesus was referring to a group of people who were alive when he foretold his prophecy and who lived to see the destruction of Jerusalem. End of story.
But because the Borg has invested so much into 1914 (and were not prepared for what they might do if events failed to unfold the way they foretold), they've been reduced to lame-brained, embarassing "noo lite" which gets crazier and more ridiculous every time they open their mouth.
So sorry inbetween-----your theory as to 'how it could work' makes no sense.