Assume you mean a Native 64-bit OSX version as opposed to Bootcamp or VM Ware Fusion / Parallels Windows Guest OS capability. Would be nice, but 64-bit multi-threaded ArcGIS Desktop is more of a priority for majority of users.
With AutoCAD recently making their way back into the MacOS arena, having an ArcGIS MacOS version would allow a company to be uni-platform under Apple instead remaining victims to Windows and its security flaws.
It'd be easier and cheaper if they just bundled a Windows license with it. I'd like to see it run on a mac, sure. But seriously, the cost of a windows license is pale compared to Arc/Info. I can't imagine how much it would cost to port. I'd say 64 bit support first. Then Mac support.
But just think of the youth market coming down the pipeline who use Macintosh and have no exposure to Windows-based machines. Over 40% of entering first year students bring Macintoshes to colllege. They won't want to deal with the enduring crankiness of Windows, so ESRI should anticipate its emerging market. So let's update from ArcView 3.1 to an OSX native ArcGIS!
I see the following has been promoted, can ESRI confirm that this is under consideration or promoted in that ESRI is currently developing an Mac version of ArcGIS Desktop
This is one of those ideas that exists for catharsis and not much else. I would love to eat my words on this one, but I don't think I will. There was no chance Esri would migrate ArcMap/ArcCatalog to MacOS. If there was a time to support MacOS, ArcGIS Pro would have been the logical time since it was a completely new product (mostly new with some guts moved forward), but we didn't see that.