Also, there are still many, many, many more PHP and Java developers and shops out there than there are Rails. That shift is far from done.
Once the good ideas have become mainstream, the work on those are done, but by then I'm sure even better ideas are available and the process starts anew.
This is not bad, this is healthy.
Don't get me wrong, I have worked with Rails - I admire what 37s have done and a good rate of churn in new ideas in any profession can be healthy and welcome thing.
I just wonder if 37s have gone from being the underdogs? What do you rebel against when you are the status quo - at least among the opinion formers and alpha geeks?
It is like when a renegade leftfield music act become mainstream. Look at Rage Against the Machine (with their leftist anti-capitalist music) becoming millionaires after signing up to one of the biggest capitalist music corporations on the planet.