I agree with the example of the macro usage of thy->thee->you/your as being an instance of progression, but I don't see the current trends in internet slang as a parallel example of something that will have such a long lasting effect on our language as a whole, but instead, well, just what I said, I see it as a trend that will eventually be a ghost. This is a prediction, of course.

it's called pro-gress. the optimistic interpretation is for a move to the better