The Btrfs (B-Tree) file system is available as a Technology Preview in Red Hat Enterprise Linux 7.
Red Hat Enterprise Linux 7.4 introduced the last planned update to this feature. Btrfs has been deprecated, which means Red Hat will not be moving Btrfs to a fully supported feature and it will be removed in a future major release of Red Hat Enterprise Linux.
Canonical already sought legal advice to permit their use of CDDL-licenced ZFS in their Ubuntu distribution; I wonder if Red Hat will attempt something similar in the future?
Given many of the XFS maintainers now work at Red Hat, it seems likely they’ll keep using that instead; perhaps even extend it. The performance is fantastic, but for data integrity ZFS is still without peer. Including, sadly, Apple’s new APFS.