Trump predicts exoneration in Russia probe as allies fear 'meltdown'
"The President seems so convinced of his impending exoneration that he is telling associates Mueller will soon write a letter clearing him."
He, after all, has already admitted to having fired Comey to alleviate the "great pressure" of the Russia investigation. I don't think Mueller can issue a statement saying that was totally not obstruction. That incident will always be hanging in the air, whether it results in a formal accusation or not.
Moreover, there's that memo that Trump dictated for Junior to mislead everyone about his meeting with the Russian lawyer. Unless Mueller can clear him of having done that (unlikely), there can be no clean bill of health, because Junior's meeting was a clearly established instance of collusion with Russia to influence the election, the very raison d'être of Mueller's appointment. (Hence any attempt to cover that up could be viewed as obstruction.)
It is very possible that no charges or conclusions from the special counsel's office will mention the President, but on the other hand, it is simply impossible for the counsel to issue a blanket exoneration.
Which means you can expect Trump to go ballistic when somebody explains that to him.
(Although I expect he'll throw a much bigger fit when Junior and Kushner start coming into Mueller's focus. Mueller let Flynn, a genuinely bad dude who could have gone to prison for the rest of his life, plead out to a minor bullshit charge, so the ol' general-turned-canary must have a very interesting tune to sing. I think that means trouble for Kushner.)