Sorry I was severely jetlagged when I posted that and don't remember wth I was thinking.
At any rate, I don't see mobile-first making Rails irrelevant. Rails has never been cutting edge on front-end development except at the very very beginning when they bundled the brand-new Prototype library. But by the time they hit 1.0, seven years ago or whatever it was, they were already going down dead-end alleys like RJS in an attempt to avoid javascript. Since then Rails hasn't done anything amazing with front-end development, but they've stayed relevant in their own way with the asset pipeline, coffeescript, and generally staying out of your way to implement whatever front-end strategy you like.
Server-side development isn't going anywhere, so I don't see how the shift to mobile makes Rails irrelevant.
At any rate, I don't see mobile-first making Rails irrelevant. Rails has never been cutting edge on front-end development except at the very very beginning when they bundled the brand-new Prototype library. But by the time they hit 1.0, seven years ago or whatever it was, they were already going down dead-end alleys like RJS in an attempt to avoid javascript. Since then Rails hasn't done anything amazing with front-end development, but they've stayed relevant in their own way with the asset pipeline, coffeescript, and generally staying out of your way to implement whatever front-end strategy you like.
Server-side development isn't going anywhere, so I don't see how the shift to mobile makes Rails irrelevant.