Here's an article from the FreeBSD mailing lists:
'The Future of ZFS in FreeBSD'

Most of it goes straight above my head, but the following sounds very interesting:

QuoteIn the past few years the vast majority of new development in ZFS has taken place in DelphixOS and zfsonlinux (ZoL). Earlier this year Delphix announced that they will be moving to ZoL https://www.delphix.com/blog/kickoff-future-eko-2018 This shift means that there will be little to no net new development of Illumos. While working through the git history of ZoL I have also discovered that many races and locking bugs have been fixed in ZoL and never made it back to Illumos and thus FreeBSD. This state of affairs has led to a general agreement among the stakeholders that I have spoken to that it makes sense to rebase FreeBSD's ZFS on ZoL. Brian Behlendorf has graciously encouraged me to add FreeBSD support directly to ZoL https://github.com/zfsonfreebsd/ZoF so that we might all have a single shared code base.

... so, ZoL not only caught up (it still hasn't reached 1.0, but still) with the rest of the Open-ZFS project, but it sounds like it's leading it right now. This is VERY exciting news (I mean, it's news to me), since I can't wait to migrate to a root on ZFS system, and it doesn't look like FreeBSD's becoming a desktop system answering my needs (yeah, gaming included) any time soon....