xz-utils are meant to supersede lzma.
Even though they're still in beta, automake is already able
to use them to create tar.xz tarballs.
Those two packages can't be installed side by side,
cause while there's no conflict on either lib or headers level,
old tools are still provided by the new package.

As it seems that there's a pretty good chance that there will be
a non-beta release before planned Gnome 2.30 release,
adding support seems like a good idea.

To make things clear, I'm talking about support for lzma compressed
files through the new lib.