My point is that the supply of RoR engineers is limited and dwindling. It’s not sustainable long term. Maybe 37Signals thinks otherwise…

You’re wrong, Rails is still very much alive. Also the idea of x language developer is outdated, as long as you know the language and framework and have done more than nothing with it there’s more flexibility these days especially for senior engineers.

Rails may very much be alive, but this thread began because strong RoR experience is mandatory for this role. This isn’t a generic discussion.