For antitrust reasons, I don't think Microsoft will stop making Office for Mac. The existence of OSX helps Microsoft fend off antitrust lawsuits and/or legislation, so it's unlikely that Microsoft would kill Office for Mac unless OSX achieved significant market share (say 20%, a very unlikely scenario unfortunately). I also recall that the original antitrust lawsuit alleged that Microsoft maintained an illegal monopoly with Office. Those allegations were eventually dropped. The fact that Microsoft makes a second version of Office (for Mac) indirectly helps stave off a resurrection of that lawsuit.
Apple Preparing for a Microsoft Free Future?