The reason I can't agree with that is this: sakura went with tsunade, Naruto went with jiraya so kakashi and sasuke would have had plenty of 1 on 1 training sessions without interference from Naruto or sakura. Plus kakashi doesn't play around.he probably would be just as strong but wouldn't have developed that much in that 2 year gap like before but i still think he would have been as strong as now because he would have still fought itachi and gotten the ms and someone from the hidden leave like a medical ninja can just transplant them,