We probably won't see XFS in the kernel for a while because the kernel patch is very intrusive, it adds a whole new layer to it - nobody seems to like that... Rik van Riel put it like this : They didn't port XFS to Linux, but rather ported Linux to XFS. Also as I recall, the XFS tools are nonfree, right ? Which might pose as a problem for distros like Debian.Btw, I noticed while going through the lk mailing list that there was a status report for 2.5.3xxx and it mentioned that ReiserFS and XFS support might be placed into the kernel at some point; I think it'd kick butt if the next (after Woody) release of Debian would allow you to choose between Reiser, ext3, and XFS when you installed it. (mmmm...XFS...*drool*)
On the other hand we have JFS which will be included in the development branch within a limited timescope.