There's been no feasibility investigation regarding porting Sentinel to Mac, and a big part of that is because we don't have anyone who knows Mac. Beyond that, there's the issue of City of Heroes being run through the Cider emulation layer, which may very well cause headaches when attempting to bring Sentinel's functionality to that platform.
We'd like to eventually look into it, but even if/when that happens, I'd err on the side of caution and say that I wouldn't expect any Sentinel on Mac--not in the near future, and depending on the circumstances that are beyond our control, maybe never.
