The Browser manages HTML, CSS and JavaScript and provides Developer Tools to debug and manage these languages. When you build with a javascript framework, you package a user experience that is entirely run by the browser, only to dispatch and save to the server when necessary.
I doubt there is a future for "backend SPA" frameworks- no one will take seriously the idea of, instead of two REST calls to get and put data, every client must connect through a socket to manage user input. Surely that will dramatically increase server bandwidth, and ignite the same type of "bloat" arguments that SPA critics use.