I'm betting that Windows is somehow going to manage to fuck this up and kill the game with either stupid updates or by doing something likewise stupid.
I honestly hope they don't, it's a fun game, it doesn't really have staying power because theres only so many times you can go into servers and build giant penises of obsidian but still, it's enjoyable and people are still buying it.
Although I really do doubt that the company was worth 2.5 billion. If you do the math, averaging the amount of money they made per copy of minecraft to about $34-$36(what with price changes from beta to alpha and release, console ports, the prices are all over the place), the game has sold about 54 million copies at last count (which is a month off, so it's obviously a bit higher, I used 56 million, seemed like a reasonable estimate.
That gives use about 1.9 billion dollars from minecraft. Obviously mojang in general has made sales from other merchandise, which means the number is a bit higher, maybe about $2.1 billion in total? Number is obviously off, because the price of minecraft has changed from alpha to beta to release and then console ports and whatnot, but it's just approximate. Could be higher, could be lower.
I obviously don't know the sales of other items that mojang has sold (like t-shirts and stuffed things) but I'm just guessing. Mojang pretty much doubled the profit they made from Minecraft in a second. My math is probably off by a lot, but still, it's somewhat closeish depending on how you look at it.