It's very interesting that MS supposedly won't make an Android version. Perhaps the iPad version is for MS to work out the kinks in mobile Office and prep it for their own Metro tablet and Windows phone. Why muddy up the waters by offering it for too many other platforms right away?
I think it's more to do with all the different versions of Android and compatibility. It also probably has to do with Androids market share in full featured tablets (i.e. non-nook or fire).