As 
lennaert mentioned —:
ou can extend a nodejs server with webrtc :)
So it's already possible to have a server connection through websocket, and it's likely also possible that you'll be able to have a webRTC connexion going through a server anyway.
Also I have to disagree a bit with your previous statement.
Yes, it's cheap to have a virtual server, yes it's "kind of easy" to set up, but tbh, not all games' scope require such a financial/technical/time investment.
Also, there's nothing wrong in designing your game to be p2p between two players only/directly and skipping the server part.
That's what most C2's customers so far were waiting for since they are not devs and don't necessary want/can be asked to learn complex networking.
Also, the promise of webRTC is that a client made in C2 can as well work as a server, and so you can program it all in C2.
Sure for a "AAA expert commercial product" this might not cut it.
For an indy/hobbyist game made for fun/to have fun, it is more than enough.