I think its far more likely that he will replace Rod Rosenstein (by hiring a new attorney general) and put a "Trumpian" in his place. With the new person in there he can (by proxy) obstruct the Mueller investigation and slowly but surely make it irrelevant. Its exactly what he did to the House investigation (using pawns like Devin Nunes.) Does Trump even have the ability to fire Mueller anyway? I thought only Rod Rodenstein could do it.