Judging the outcome of a fight based on abilities of given characters is one way of predicting the results. It can be fun and in-universe seems the most logical, but you should also ask yourself - "What would such an outcome mean for the story of the series?"
Before I get to the point, let me rollback to a time before Tobi's identity was revealed.
Obito was not the most frequent prediction and that's because no one thought about the plot.
What would happen in the manga if Tobi was revealed to be Kagami or Izuna?
ABSOLUTELY NOTHING.
No characters present in the battlefield could recognize them. Such "Tobi" would also be a totally new character for the readers, which would mean they wouldn't really care that much. Emotional aspect of Tobi's identity reveal would be gone.
When Obito was revealed, however, the fans were VERY excited about this - some were happy, some of them raged, but EVERYONE was touched by this moment.
Obito was the most obvious answer when taking into account an argument from plot, yet few people accepted this as a valid argument.
Let's move on - Tobi's identity has been revealed, so what should be Obito's "epic" battle now? Naruto VS Obito? Of course, if this wasn't just a manga, then this fight would be "chosen" randomly - Obito could fight Naruto or Bee or whomever.
BUT this is manga. Many of the fights are picked in such a way that they are the most personal. Naruto VS Sasuke, Jirayia VS Pain, even such less important ones like Hinata VS Neji in the first part. Kakashi's past has been a heavy burden to him, so it is only logical that he would be the one to deal with Obito.
And look, that's what's going to happen. Again it's the plot that determines the events of the manga.
And now we come to predicting the outcome of this battle. Many people are eager to yell "KAKASHI'S GONNA DIE, HE HAS NO CHANCES", but is it really going to happen? What would be the consequences of this for story development? You think Kishimoto would just make a third main character (after Naruto and Sasuke) die when pitted against his own past? That's right, Obito represents Kakashi's past and the heavy burden he had to carry ever since before the series started. A main character being defeated by his own weaknesses is definitely not a theme of ANY shonen manga and Naruto is no exception.
All in all, Kakashi will not be defeated. He will either win or persuade Obito to redeem - which would be another form of victory and overcoming his past.
And if you start saying that it would be a huge asspull because Kakashi's abilities are inferior to that of Obito's (even though I could argue about this one), then remember one final thing:
It is characters' abilities that adjust to the needs of the story, not the other way around.
Cheer!
