Well, very hard to tell... It's not like Kakashi would stand there and watch himself being hit by Muus attack. If Kakashi once has trace of Muu, he has a real chance. Muus sensory ability won't be able do differ Kage Bushin from real Kakashi. But its true, i dont's see much was Kakashi could take the offensive, only counters would be an option. But on the other side, Muu keeping his distanz by flying and spaming Jinton wont bring him the victory either. Do not underestimate Kakashis speed.
Those who are saying Kakashi surly are optimists, but those who criticize the ones saying Kakashi as it happened here before, are to ignorant in my opinion.