Like everything...
Call me when it's in there and it works and I can use it. Until then, it's nothing more than hyperbole.
There was nothing stopping this happening 5 years ago, there's nothing stopping it happening now. Even as a GPLv2-licensed kernel fork, without going through proper submission, it would slowly creep across if it was that useful.
Fact is, though I'd have trusted Sun to do so, and to bring this across, Oracle more often than not ends up as a curator of someone else's code that they deemed destructive to their business so they bought them up. Everything they touch gets forked and the fork is - without exception - better. I can't believe that ZFS is any different. They'll dump it on someone when they no longer can be bothered with it, which is what it sounds like they are heading towards. Maybe some ZFSv2 Linux spin-off will actually make it into the kernel, with some kind of better performance, ideas, avoiding patents, etc. but that's decades away.
And the anecdote about being told "use that broken stuff, no you can't go back despite having myriad problems"? Way to run a business? I don't think so. That doesn't inspire me with confidence at all. The story should be "the person came in and insisted we move to ZFS - against other's people's wishes because it was 'too early' - because they'd secretly trialled it alongside their existing system and it performed better than anything else". Not "It was a heap of junk but we're gonna make you use it and we'll just throw you a few developers so your live-system can act as an alpha test and be patched as we find the bugs that you're constantly running across".