Ruminations on the future of ZFS
The big news recently has been Jonathan Schwartz saying that he regrets not GPL'ing ZFS, on the implied grounds that ZFS being in Linux would have made it relevant. Setting aside questions about whether or not GPL'ing ZFS would have worked to get it included in Linux and whether it would have been a good idea for Sun, this leads naturally to thoughts about ZFS's future.
ZFS's future is intertwined with the futures of Solaris and Illumos. Solaris's future is entangled with Oracle and so essentially opaque, but my personal opinion is that Solaris is basically dead as far as ZFS developments go (and probably in general, although Oracle will keep shaking the corpse for a while). That leaves Illumos. The problem with Illumos, put simply, is that it's a free Unix without an ecological niche. Not many people are interested in Illumos or any derived version for its own sake and it seems unlikely that that will change (the ecological niches that Illumos could plausibly make a play for are solidly occupied by strong Unixes). This effectively leaves ZFS development being done by a consortium of storage appliance vendors and storage users.
(I am discounting FreeBSD here because it's not clear if FreeBSD is doing any independent ZFS development.)
The problem with this is that historically, niche Unixes and niche Unix projects have had problems sustaining themselves and keeping development happening (due to both lack of resources and being insufficiently attractive to most outside developers). And indeed right now ZFS seems to be mostly frozen. This has advantages, such as a selection of platforms to get equivalent versions of ZFS on, but it also has significant drawbacks because ZFS is still missing important features (the most prominent is the ability to remove vdevs from a pool, which matters for long term storage management).
So the much shorter version of this is that the future of ZFS right now certainly seems to be ZFS as a slow-moving thing. Whether or not it's entirely a niche thing isolated in what is essentially a backwater depends on FreeBSD (and I have no idea how much the FreeBSD people like ZFS).
(A related issue is that ZFS is mostly standing still while other potential competitors advance. The potential competitors are starting from well behind where ZFS is now, but we've seen this show before and it didn't end well for the incumbent commercial Unixes.)
Sidebar: Why I consider Solaris dead for ZFS
It's a combination of three things. First, apparently almost all of the original ZFS developers have left Oracle (many of them have wound up working on Illumos). Second, Solaris is no longer open source, so any ZFS developments that happen there are a closed box. Third, Oracle's pricing on Solaris makes it unattractive for most people to run, so whatever closed-box ZFS changes that happen are not going to be widely used.