"The generation that saw 1914, taking into account the new understanding of an overlapping generation being a better interpretation, hasn't passed away yet. If it does, then the WT will have been proven to be a false prophet."
To the OP - This is a typical rhetorical fallacy. The society uses "increased light" - which...by the way (Proverbs 4:18)....is a scripture taken grossly out of context that allows them to make whatever interpretations and predictions they want to, knowing they can always change it again later if they want to......as a safety net for false teachings.
With the use of Proverbs 4:18, the society has, does and will change teachings on a whim and say that "new light has been shed on the matter". This explanation prevents them from ever having to own up to past false falsehoods. Seriously, try to be objective here. Think about what you wrote (that I quoted) above. Their interpretation of what constitutes a generation (70 to 80 years) and how it relates to the year 1914 FAILED. It wasn't until AFTER the failure that they re-worked their definition.....and then another 15 years after that, that we ended up with the "overlapping generation" definition. The "overlapping generation" explanation was the result of the FAILURE of their previous explanation.
Do you really think that 50 years from now.....when the overlapping generation explanation proves to be false.....that will be it? Do you really think the society will say "well.....we were wrong. Darn it!" Be reasonable! There will be a brand new explanation that makes the current understanding "old light". And all the witnesses will go on believing the new understanding while echoing your sentiments.....saying "see? it wasn't a failed prophecy....it was increased light!!!!! Aren't we thankful for Jehovah's progressive light?" You see.....there will always be a new explanation to take the place of the immediate past one that failed. As such......there will never be an admission to prophecy failure.
If the society can chalk past failures of their predictions up to old light.......then can't anyone?
I once predicted that Hillary Clinton would become President 2008. As it turns out....she didn't. But was I wrong? No! The statistics I had and the information I was relying on was "old light". The old light caused me to have "premature expectations". New light was quickly shed and Obama was given the democratic nomination. Ever thankful for increasing light....I revised my estimation and said that Barack Obama would be president. And Look! I was right! It is clear that Jehovah directed it.
If I use the same reasoning that you allow the society to use.....then I've never been wrong in my life. I've just had a few "unrealized expectations" that were cleared up once "new light" was shed on the matter.