It's a good question. If you believe that whatever happens to Obito's eye also happens to Kakashi's, which is what I believe, then we'll find out next chapter. In the last chapter Obito still had 2 tomoe, and if Rin's death activates MS, I'm guessing the 3rd will somehow pop out before MS activation. But what do I know, I've been unsuccessfully trying to unlock my sharingan for years now.