Mojang will be rolling out an update to Minecraft on February 4th 2015 that will allow you to change your in-game name.
It won’t cost any money to change your name but you will only be able to pick a unique one; that is, one that isn’t already taken. You can arrange to have someone else’s in-game name with them, but you will have to wait 37 days before it becomes available for you to take.
Once the feature is available in early February, you should see an option to change your in-game name in your account page. The only thing you will need is a Mojang account, which you should have if you sign into Minecraft with an email address anyway. It’s possible to migrate older Minecraft accounts here.
Once your username has been changed, you will not be able to change it again for another 30 days, otherwise there are no limitations on how many times you can change it. And, of course, you’ll keep all inventory, pets, statistics, and so on across all servers if and when you do change your username.
In related news, Minecraft: Pocket Edition has sold over 30 million copies now. And it seems that Minecraft is probably the most popular PC game based entirely on concurrent players, as Mojang’s Nathan Adams tweeted that during off-peak times the game has about one million players, beating Valve’s Dota 2 statistics by a wide margin.
That’s only Minecraft players on PC, and doesn’t include players of the console and mobile versions, nor does it count people playing older and pirated versions of the game.