My experience with microsoft windows was so bad that I will not use their operating systems. Even when I did, every other release was a disaster. 95 - good; 98; bad. 98 second edition: good, ME, bad. In the NT kernel world, much the same.
My experience with Skype, now that microsoft has bought it? They recently forced everyone to upgrade, claiming that the older clients were no longer compatible ... except that my old PPC client is just happy and fine. It has no ads. The older intel clients had no ads -- they date from when Skype was trying to sell phone time. Now? New client wants to display ads at login; new ToS basically lets Microsoft do anything they want with our conversations. Hmm.
My experience with other microsoft products? They've gone from "sell it once" to "sell an ongoing subscription". They've implemented "Change the save format, so people with older versions can't work with it, and have to buy new versions just to share with you". They push updates with "features" that very few people actually need.
My expectation if Microsoft buys Mojang? ... Sure, Minecraft on windows devices, that's a given. Scrolls ... I can see Scrolls moving to a "milk more money" model, maybe even giving the game away for 99 cents, or free -- and requring purchases to make more advances. Actually, that's a good reason to hold off on the game -- I'd rather wait, and make sure that there's no disaster change in the model of the game before I buy.
I can certainly see the realms system expanded, big-time, and made cheaper; with the goal of putting all competing low-cost hosting services out of business.
Do I expect them to kill modding? No. If they did, or even tried, then there would be a good working clone of the game within months. They don't want that; they'll keep modding available. But I wonder what kind of license their modding API will have, and what modders will have to do. Right now, for example, Mojang does not require your source code, but I can see Microsoft, in the same view as their app store, saying "we need to see your code before we'll approve your mod". Combine that with the existing "we can redistribute your mod or any part of your mod" ...
I expect paid-mods. Just like their app store. But you'll have to sell your mod through their site, and they take a percentage.
How will they make that 2 billion back? Pennies here, pennies there. Volume. Lots of pennies from scrolls, from mods, etc. Very very high volume.