It’s very close to feature complete; at that point there will be a general call for developers to opt-in to the release as it progresses through 42.x releases until no more bugs have been found.
If you’d like to live a little more dangerously, we can move devices to 41.x now for you to get started on development; the UDP features are complete and have been for many months. Other customers have been doing this for development of their local networking features.