Joss Whedon has no plans of creating this show whatsoever, and I don't think that there will ever be more released of the Buffy-verse than Buffy Season 8 and ANGEL: After the Fall.
Joss has had many ideas of creating more, because we fans are eager and we love the Buff-verse. Now with Dollhouse about to be aired, and the many comic books that he is working on, I doubt that this show will ever be more than just a rumour. Joss hasn't said anything about this shows in years, so I doubt it'll ever come to it.
Sadly, because I would have loved to see it.