CyanogenMod 9 may still be a ways out, lending some credence to the claim that upgrading from Gingerbread to ICS is a very long endeavor. However, if you're willing to live your life on the bleeding edge, and you own an international Galaxy S III variant, then the time is right for you: CM9 nightlies are now available for your device.
This is, of course, still an early build, so expect some bugs along the way. CM9 has still not reached release candidate stage yet, which is itself still a few steps away from stable release. The adventurous and the knowledgeable need not concern themselves, though.