coordinating bash and coreutils: which bash?

[Paul Eggert]

A few months ago we went through a POSIX-compatibility sweep of
coreutils, and in my nonexistent spare time I'd like to migrate some
of those fixes into the Bash builtins that duplicate coreutils.
Conversely, I'd like to migrate any fixes made by Bash in this area
into coreutils.

Which version of Bash should I use to do this?  I vaguely recall that
an alpha or beta version was released recently, but I can't find this
announcement on the Web, nor could I find recent sources when I poked
around in the obvious FTP or CVS places.

Thanks.