I think a lot of developers focus on learning newer technology stacks because they are hot and tend to pay more. But less popular doesn't mean it's not in demand.
I know 2 COBOL programmers who are being paid a ton of money because of critical banking systems running it and candidates are hard to find.
If you look at the trend for 'rails' it's much more level and googling 'rails' three of the top four results are for the framework. It may be people no longer have to type 'ruby on...'.
