I never took the time to try WebSockets, so please forgive me if this question doesn't make sense, but, does HTTP/2 supersedes WebSockets? I'm under the impression that HTTP/2 covers all the WebSockets' use cases, is this a correct observation?
Websockets are still important if you need something like real-time input-event streaming (e.g. for an online game); a properly-structured binary protocol sent over a websocket will be much lower-overhead than the equivalent HTTP/2 frames.
If you use WebSockets for "realtime push", then HTTP/2's server push feature could potentially be used as an alternative (though I've not heard of anyone actually doing this yet).
If you use WebSockets because you actually want a bidirectional message-oriented transport protocol, well then you'll keep using WebSockets. :)
One thing to keep in mind with HTTP/2 server push is that a server can only send a push in response to a client request. So this isn't a drop-in "real-time push" mechanism. To implement the equivalent of real-time push would likely require client/server to keep a stream within the connection in the "open" state whereby the server can send continue to send data frames on that.
One thing to keep in mind with HTTP/2 server push is that a server can only
send a push in response to a client request.