As far as I know, all that they have verified is that it will come out for both Macs and PCs, a substantial time after it is released for the X-Box. Since Oni was released with semi-OS X support (as in, it sort of works), and Bungie was the developer of Oni for the most it's development cycle, I think it would be a healthy prediction that OS X support is likely.
Since I've mentioned Oni, does anyone know the deal with
this page? The Omni Group appears to be working on a new, and most likely Cocoa, version of it. I don't seem to remember hearing this being reported at all.