Karl Magnus Troedsson has evidently said that mod tools are a possibility still for BF3.  He said they definitely won't be in at launch, but they may possibly be implemented later.  Here's the quote:
 

“I will say that there’s been a lot of cool things coming out of the mod community for many years; I have a lot of respect for the people in the mod community, at the same time, as developers of a game of this magnitude — I mean, it’s the biggest thing we’ve ever done — we have to select what it is we’re going to spend our focus on. We cannot do everything; it’s basically like that.”

“We have heard the community very loud and clear on this topic — that they want mod tools, we are considering it, back in the studio. The game won’t ship with mod tools, but we have heard it. I’m not saying that we’re going to do it, I’m saying that we are thinking about it.”

No clue why that double posted... please lock the other one up!

Actually this one's getting more views and I'm gonna reply to it, so you should change your post to "lock up the other one, mods" :P 
 
And yes, when he says they're thinking about it, it means it's paid DLC

Isn't "its under consideration" PR speak for "its not under consideration at all"? Maybe I've just become too jaded over the years.

it's a move to give hope to people who are potentially on the fence and are hinging their purchase on whether mod tools will be available or not.  Showing some hope to people is a significant thing, even though he later notes that it doesn't mean the tools will be released. Just hinting that it is a serious topic and is being considered for release, is more than enough hope for those potentially on the fence.   
 
It's an important press release because now in online discussions of games, people who use the "BF3 sucks, it won't even have mod tools" , will be attacked by the BF3 supporters with a weapon of "DICE got mod tools in their sight" ... shit like this. So fanboys can convince non-fanboys to buy into BF3.... potentially of course.

@AhmadMetallic said:

Actually this one's getting more views and I'm gonna reply to it, so you should change your post to "lock up the other one, mods" :P And yes, when he says they're thinking about it, it means it's paid DLC

Which I'm fine with. Not every wants or needs Mod tools. So their focus should be on things that everyone needs and wants, like an integrated server browser for one.