this would seem more likely to release something major in a year, compared to 6 months. That would be about 4-6 months ahead of schedule for Apple. I could definitely see 10.6 features being previewed and a developer release. This would probably be needed for the transition away from HFS+ to ZFS. Plus zfs still has a long way to go, they are only on build 117 and do not have every bug worked out. Plus Apple has had to redesign the Finder, Spotlight, Time Machine, etc. just to name a few features, for zfs. I could see a tarball update for zfs in 10.5 if someone was really smart, after WWDC.