Mojang have just made the 1.7.6 patch for Minecraft live. Although there’s no player facing changes to talk about, it does include the tech required for renaming your player character.
The renaming feature will be made live at a later date, alongside a new system for handling player skins.
Players running previous versions of the game will not be able to enter any servers running 1.7.6, and Mojang want players to be aware that it is not possible to switch a server between offline, and online modes, “... because profiles are not compatible between these two server modes.”
Got all that? The server files are available from Mojang.