To my mind the big news is Turbolink, A simple tech to build SPA with the following roots :
- the robustness & ecosystem of the rails server side (great testing stack & battle tested backend)
- the lightweight approach of rails/javascript, which is opting out of jquery : meaning that SPAs won't have to include jQuery and the whole JS world (client side speed will be greatly enhanced)
- the overall simplicity (no huge javascript stack pilling angular, react, redux, flux, webpack etc...).
That's rad.