That creepy graphic looks like a giraffe's neck.
I think that this grammar analogy is nearly done to death, but it has occurred to me that the problem stems from the fact we have not properly defined our terms.
We need to consider what the purpose of language is, and it is to communicate. Language is one, and only one, of the ways in which we communicate. There are many languages, all of which have their own rules for both the written and spoken languages. I think you may not be a native english speaker, Zeph, as you refer to the need to adapt to new words and so the rules change. In English the absorption of new words has never been a problem, there are rules but they are very, very fluid. That makes English an extremely difficult language to learn to fluency, but it is also a language that eagerly absorbs foreign words, often without anglisising them. It also goes without saying that written language has stricter and more formal rules.
Then there is also non-verbal communication- that requires no explanation. We have all just seen a stunning example of that in the Opening Ceremony of the Games. I understand not one word of Chinese, but I understood that dramatic presentation. Gesture, facial expression, graphics, pictures etc are all part of non-verbal communication.
Thus I suggest that language as a predictor, or even a model, of Phase Shift is too restrictive. Music, as we learned on Friday, is universal, and so is mathematics. Either of those would illustrate Phase Shift with much greater clarity.
But to go back to the original proposition. I feel that the shift to Civilisation 1 will have to be something original, not a logical development of observable markers. Something like the comet that killed the dinosaurs and allowed the mammals to fill an evolutionary niche that did not include being a tasty dinner for large lizards!
(The above is a statement of my own views, of course, so sorry to all creationists----just cover your eyes!)