Today, the ZFS repository on MacOSforge was closed, likely meaning the end of Apple’s pursuit of Sun’s next generation file storage system for use in Mac and Macintosh OSX Server. They also mention that the mailing list and repository are also being removed.
As John Gruber points out, the writing has been on the wall for awhile as 10.6 betas had some support for the file system but the final releases (Client and Server) had it wiped from existence.
While it is now unlikely that Apple will ever use ZFS as a mainstream file system, it is possible that Apple could support it as a third party file system, like it does with SMB or NFS formats. Gruber mentions that this decision was more of a legal one than a technical one. Perhaps Sun’s new owner, Oracle (not a big open source player), wants to keep the technology in-house. He also mentioned that Apple is hiring internal file systems engineers, meaning they are going to build their own next-gen file system.