That's my line of thought to. I think this will put the security through obscurity debate to test.You're paying too much attention to the quantity of the target rather than the desirability of the target. China was not hacking Google because they were using Windows. They were hacking Windows because Google was using it. Now there will be incentive for the hackers to learn to hack OS X.
I'm guessing Google will probably be issuing the Chrome browser to their users as opposed to Safari. It is curious why Google wouldn't have just made all their employees use Chrome on Windows, since I thought Chrome on Windows is very secure compared to IE and Firefox.