The sale is going to happen, when the Wall street journal reports that a sale is happening it will..
However I think it's a mistake. With the type of game that Minecraft is, what can they really do in a Minecraft 2? Honestly the creator of Minecraft said he would never do this, yet here he is. I'm wondering if he is just realizing there is nothing else that he can do, and seeing Microsoft offer 2 billion, he is saying, heck yea and running away with it.
Had Microsoft done this a year or so ago and made Minecraft an Xbox one exclusive then it would have made sense, otherwise I think it's a bad move.