there is a gettext plugin where you actually just send the translation files as js files :) basically generating a multidimensional hashmap.
-> en.js
reduces the payload but we could argue about a catalogue based page and based on your system you need to build your own parser to generate those file. actually I'm doing that atm to unify my *.volt, *.php, *.js files
but I want to be unified because I only wanna maintain 1 catalogue there are newer approaches esp. for JS.
so i18n still is alive :) in short