安定版へのアップグレードに最適な時期は今ですか？

[Canapin (Coin-coin le Canapin)]

stable と test-passed の良い説明です。

Is Discourse always in "beta"?

There’s a good explanation of the branches we use here: So Discourse is in a perpetual beta state, meaning that we’re always working on new features and refinement. In our case beta does not mean unstable; we host sites with millions of monthly pageviews on our tests-passed and beta versions.