Putting on my Carnac hat here.
Let's say the evidence for evolution becomes so overwhelming that the Society eventually has to accept it due to much turmoil in the congregations.
How do they do so without saying they've been wrong?
Why, redefine a word, of course! Just like they did with "Generation," they can redefine the word "Kind."
The Society uses this word "Kind" to refer to the different types of animals on the earth.
The Biblical “kinds” seem to constitute divisions of life-forms wherein each division allows for cross-fertility within its limits. If so, then the boundary between “kinds” is to be drawn at the point where fertilization ceases to occur.
So, here's how they could go about redefining it.
They come up with the doctrine of **OVERLAPPING** kinds!
"Oh see, that whale and hippo may have come from a common ancestor, but that's because they are overlapping 'kinds.' That doesn't prove creation didn't happen!"Overlap is the new Magic Bullet.
"You still haven't shown one 'kind' changing to another...they're overlapping, so they're the same."
"See, when jehovah created the first single cell organism billions of years ago, he caused it to divide into different kinds. After all, doesn't his name mean 'he causes to become?'"
"After that point, those kinds went through adaptation based on their environments...and that's why we have various species today. An ape and a human are the same 'kind.' You'll never see a human turn into a shark! Shark's aren't the same 'kind.'"
"It's really very simple! Here let me show you. Pretend the root of this tree is the first single cell organism created by Jehovah. Then, Jehovah caused it to branch off into different "kinds." Those kinds continued to branch, and though they created more branches, they never created more "kinds" because they came from that same branch. **Don't you see? The bible is scientific!**"