Scala 2.13.0-RC1 further refines and polishes the new collections API, among other improvements.
If no major problems are found in this release candidate, we will re-release it as 2.13.0. In the meantime, we’ll be working primarily on documentation and on helping the ecosystem upgrade.
For details, see the release notes: https://github.com/scala/scala/releases/tag/v2.13.0-RC1
Core libraries are already available for RC1; more are coming. Watch https://github.com/scala/make-release-notes/blob/2.13.x/projects-2.13.md