Jenkinsph--Good post and clear thinking. I too used to think there would be no more gear transmissions at some point but no longer completely think so and believe i was guilty of the "linear" thinking that got me confused in the past. That is, we take was is occurring. and at the rate it is occurring and project that rate forward for a degree of infinity. No cyclical consideration is given and the trend is your friend.
What I beieve I have learned, however is there is an absolute need for the gear transmission in many agricultural and other applications, perhaps moreso than a hydro. For the hobby market, hydro is great because there is little learning curve and the uninitiated are nearly immediately proficient. Also true on the big tractor CVT and farming 5000 acres; it's simpliy easier with less hassle and a gear drive is not really needed--but maintaing RPM is.
In the middle is everyone else and that's a huge segment of the market. Gear drive synchro with reverser is a relatively new innovation and I think is a desirable combination that will be around a long time. It works well for utility ag purposes and that's the largest part of the tractor market. See, I was a 100% hydro convert but recently bought a Kubota MX5100 gear-hydro for utility ag/landscape uses and did so because experience has shown me it was the better option. So it's a big tent and there's room for us all. All tractors are good regardless if gear, hydro, CVT or even stuck in neutral.
Incedentially, I read a magazine at the doctor's offoce recently that mentioned a consumer desire to return to car handles and door lock buttons as opposed to electric options. And I can't recall the degree of demand but there was mention of an upturn in desire for the gear transmission in cars. Go figure.