While I am beyond gratified to see mathematicians getting the recognition they deserve, Terence Tao and John Milnor cannot be inducted to the OSA (S) posthumuously as neither of them are currently deceased.
(And a very good thing, too. John Milnor supremacy!)
'posthumous' inductions is a misnomer within Atlasia, I'm afraid - several Presidents before me have bestowed the honor to living politicians and other notable figures.
Well then, in that case I will simply reiterate my complete approval of your decision to recognize some of Atlasia's finest living minds in this manner.