GameStar, a German gaming magazine, posted an interview video with Patrick Söderlund from EA confirming there will be no modding tools for Battlefield 3 at launch. No other source has been able to confirm or deny any information about modding in Battlefield 3 until now.
When Gamestar asked the EA executive "...why?" Patrick simply replied,
"Because if you look at the Frostbite engine, and how complex it is, it’s going to be very difficult for people to mod the game, because of the nature of the set up of levels, of the destruction and all those things… it’s quite tricky. So we think it’s going to be too big of a challenge for people to make a mod."
Skip to the 2:00 minute mark to hear Patrick's full response regarding modding tools in BF3. This response may offend many hardcore fans because even tho modding Battlefield will be "very difficult" and "quite tricky" with such a advance engine, modders have been producing amazing content no matter how difficult since modding has become available.
Take a look at the very popular, Project Reality Mod for Battlefield 2 and see an example of what modders are capable of:
If this news upsets you, put yourself in DICE/EA's shoes. Developers must withhold any modding tools that will allow users to create their own content for at least a few months to make profit and release official DLC content.