As a relative newcomer it's certainly confusing as to why this forum software is publicized as it is.
It's marketed as "don't put this on production we won't offer support", but then the site provides a forum with a thread that says "need support? You've come to the right place!"
It goes on to have an extensions area to add extra functionality, most of which appears to be geared towards people who would use it live, and even a planned hosting service, which seems a bit pointless if the software isn't complete and shouldn't be used in production?
Heck, there is an entire thread dedicated to people who have put it live with 90 responses:
https://discuss.flarum.org/d/579-showcase-your-flarum
As an admin and user of various forum platforms, most of them are technically "beta", same as this, and although this core is basic, that's what gives it the charm, and makes it fast and usable for most people.
I think most people here can testify that it works enough to put into production, so I wouldn't worry about the release. Just use it as this magical release date may never come, you never know, you or your users (if you have some) might not like it and have wasted your time waiting. If you're in an enterprise situation where using beta software is an issue then you're better off looking elsewhere as it's unlikely there will be official support even when a release is apparent, compared to other CMS and forum platforms with fees and licensing, this is free after all.