Sorry, but there are no plans to support OS X at the moment.
Well, I would't say this is that straightforward. No doubts, algorithm-level optimization will work fine on Mac as well if achieved on Windows. TBB does great job here in terms of portability.But if you tune lower level matter, like fine-grain sycronization depending on sheduler implementations, you'll most probably observe some different behaviour because of different threading implementations (TBB wraps native threading API) and OS schedulers difference.
Thank you for asking.