Windows Server 2016 with ReFS 3.1 (it has became 3.1 in the RTM version) is certainly worth a look. If you search on these forums you will find lots of information. For example: This holds great conversations: veeam-backup-replication-f2/veeam-next-big-thing-refs-t37231-15.html
Deduplication in windows server 2016 (NTFS, no ReFS) has also received some improvements so certainly also worth the effort to try that out in your environment but as already stated, you are limited per volume with 64 TB for the volume size.
My personal preference would be to do some tests with server 2016 today, and certainly on the ReFS part. If I understand it correctly, you have until February. So the moment it hits GA, I would do some PoC testing with ReFS (for a month or so) and see what it does (my testing has already gone very well, and that was on TP5, not even on the RTM or GA version, still need to find time and do some work on the RTM version
). I personally have become a big fan of ReFS and what you can do with it in conjunction with B&R, but that also means that you need to wait for v9.5 to come out of course