The current stack I work with:

Gulp for task (test/build/etc.)

Webpack for bundeling

React/Redux for the front-end

Bootstrap for the styling

Koa for the back-end

Socket.IO for the realtime stuff

RethinkDB as the datastore

Nginx as the reverse proxy to the API and static file server

What would I change in the future?

Getting rid of Gulp, most of the time Make should be enough.

Replacing Redux, Socket.IO and Koa with the Apollo stack. GraphQL with its subscriptions solves most of the problems I had with REST and WebSocket APIs the last years.

I'd probably use Preact instead of React, because it's much smaller. The React eco-system is unbeatable, so I wouldn't switch frameworks in the near future.

Don't know about Rethink, it's a really nice DB and the change-feeds play well with GraphQL subscriptions on the other hand the company behind it went down the drain :\