It already has many features (such as volume management) that ZFS doesn't have.
What features in particular are you talking about? Personally I'm wating for proper RAID5/6 code, but other
than that I can't think of anything lacking. (Besides maybe support for raw block device export, which I don't
think is even planned).
What do you mean by 'volume management'? ZFS has datasets which are similar to 'volumes' but far, far more flexible, as well as ZVols, which are exactly as they sound like: volumes.