Considering the level of effort involved, I kind of hope there won't be one. I'd rather see that effort devoted to fixing the issues with the software we already have.
I'd also be surprised if there's much of a demand. People in our industry tend to be very cost-concious, and to get a computer of equivalent power, you have to pay quite a bit more for a Mac. So I suspect most people in our industry would not be interested in significantly higher costs, just to run software that should work just as well (if not better) on a PC. Especially since people in our industry generally don't have any Macs, and most would have to buy all new hardware, as well as retrain staff in how to use a different OS...
I tend to agree with Sinc on this one
While we can't/won't talk about what we are doing, we sometimes talk about what we're not doing. Case and point: Civil 3D running on the Mac version of AutoCAD is not in our current product plans. We have Autodesk employees that run Civil 3D on the Mac, but they are running it in either a virtual machine or have their Mac running Windows 7x64.
Get out you checkbook! http://usa.autodesk.com/adsk/servlet/pc/index?id=1
I posted too quickly. I don't see any links for Civil 3D. Only AutoCAD. I don't know if a Mac version is planned for 2012.