Patch 4.1 is live on the US realms and will go live tonight on the EU realms. While Blizzard has not removed the PTR status of the patch notes from the official site, starting up the game does reveal that the current version is indeed 4.1.
Don't forget to check for developer updates for your addons. Then, either go through your addons *.toc files interface versions to 40100 or click "Load out-of-date addons" in the options from the character selection screen in-game. The latter is usually less time consuming. The *.toc files can be found in \World of Warcraft\Interface\AddOns in their individual addons' main directory.