Are there plans to support other scripting languages next to JSR223 ?
Node.js is popular these days 
Most of the JSR223 implementations and Java integration are not complete enough for use in openHAB. That said, node.js is a server framework written in JavaScript, not a scripting language per se.
As @steve1 says, node.js is not a scripting language but a framework that one interacts with using JavaScript. That being said, there is nothing stopping you using node.js to interact with your OpenHab server via MQTT. Most of my rules are implemented in a node js script that runs on the same box as OpenHab. This is very much experimental code though.