Yep, all the old CSS tools stay. We’ll be marking a few things as deprecated (right now it’s just the old fa-stack and associated styling) and they’ll be removed in the next version. And we’re putting together a shim to go with the new SVG framework so things will just work with the new code. When folks get the time to update their code, they can do it on their own timeline.

For folks who want to roll it all themselves without using any JS, we’re also releasing the original webfont files and standard SVG sprites. We personally don’t think they’re the best way to go, but we know each person has their preferences (some being quite strong 😃). Also keep in mind, we’re being very careful with all JS. Things will be quite performant, if that’s the gotcha for you.

As for specific language support on the server side, we don’t have any hard plans just yet. But it makes a lot of sense, and we’re definitely listening carefully to requests like this. As we hear enough of them, they tend to eventually pop the priority stack. But I suspect server-side support won’t happen for a while. If folks want to release their own plug-ins my mimicing the interface, that sounds pretty cool to us. If they look right, we’d consider pulling them into the main project or making them recommended (so we don’t get multiple solutions for the same language that are hard to sort through).

And while we’re not releasing server-side support just yet, we are supporting React, Angular, Ember.js, and Vue.js (which we personally happen to be massive fans of). These will be released after 5.0.0 proper, as they’re stretch goals.