Earlier quoted context omitted.
"Ruby is by no means inferior to PHP, and you will get paid more per hour to program in Ruby." Any decision you make to learn anything based on payback has to factor in what will happen if more people choose to learn something. If more people learn Ruby because it pays better (let's assume that is correct) then supply and demand could equalize and the pay will go down. Right now if pay is high for Ruby it means most…
Right right right. I would add this: Ruby could well be considered "passé" someday (history tells us it necessarily will be), and the Rubyists of the future would really bristle at the suggestion that what they're doing is worth less simply because the market says it is.
In any event, the transition should be slow and I fully expect Ruby to be around for a long time, but people may notice a slow decline in demand for Rails programmers in the next few years compared to other hotter technologies. Sinatra (or some other Ruby framework) may replace Rails as a backend.
I'm a Rails programmer and I don't bristle at the suggestion that market demand changes. I welcome the change and adapt. I don't mind learning new languages.