And Nate, Kakashi was about to use it against Kakuzu. But Naruto & co. showed up and he didn't need to.
As for what I think is gonna happen with Kakashi, I think Madara is going to be involved somehow. In 395/396, Kakashi had the biggest reaction when he noticed his Sharingan. I don't know...that just felt like foreshadowing to me.
So he tought it to himself?
I don't doubt what you say about the timing, but I find the whole thing a bit far fetched. He can't even turn if off, but he can teach it new tricks? If this is Kishimoto's explanation then I don't buy it. Mangekyou has never been something you teach yourself to obtain. At best, it's been something to refine once obtained, but obtaining too more than training.
I still seems to me to be a watered down version rather than a true MS because, at least as of yet, he hasn't performed any of the staple Mangekyou attacks. If he does do that it'll be immensely disappointing because without a damn good explanation it just cheapens the requirement further. Reminds of what Vegeta said about Super Saiyin in the English Version, calling it a super saiyin bargain sale. It also openly contradicts what Itacchi said about it and makes those statements meaningless.