DaveX: I think there´s a misunderstanding: If he has already a steam-key it pretty much doesn´t matter if he activates it now, tomorrow, in Two weeks, or next year! The date 31.1.2017 just describes the last day to request the key at S397 - or better said: the last day where you can change your standalone account into a steam-key. Besides that AceLain is right: you can activate it now and download it later with your new system.
Well no league is going to stay with build 1098 forever, so makes no difference. Once DX11 is out, everyone will move to that and the non-Steam version will become essentially dead.
