I think he's already gone on record saying in the OT, not all of the stormtroopers are clones, and certainly aren't all based off of Jango, given that he died some 25 years earlier. Given that the clones age at twice the rate, Jango's clones would be creaking around.
Unless they're making copies of copies, which could explain why OT stormtroopers aren't all that sharp compared to PT clonetroopers.
Plus, George actually is a fan of TROOPS. And we know those troopers weren't clones.