that would be a no, it looks like the 2012 builds through March in the US at least will have the old I6 with 240 HP.
After that, it sounds like the new I4 turbo should either come mid year (not sure if they would call it a 2012 still or a 2013) or they might even wait until fall 2012 to change it. But it will not have 268 horsepower, this engine has been confirmed at 245 I think, they wouldn't make the 28i that close in power to the 35i especially since it will weigh less. Now you could probably easily tune it to get 270+ HP if you want to chance voiding your warranty.
I have just decided to wait until 2013 models to buy our X3, not that the 35i is a bad option, its a great engine, but I am more intrigued by the fuel effeciency of the new 28i, or the power and effeciency of the 35d when we finally get it. Or we might just go balls out and get the X3M, if its $65K or less fully loaded, I am hoping with a i6 it will be as I can't see paying more than that for an inline 6 engine