From a biz perspective, I don't know that they would significantly change up the packages and options like they did for 2013, including adding the individual options, just to turn right around and offer a facelift the following year.
Also, I like what another poster suggested, that they will facelift after the MB. I would do this if it were my decision. But I would do it quickly after (within four to six months), so early 2014 (as yet someone else mentioned).
So my money is on MY 2015 but early in 2014.
Current: 2015 i3 REx | Giga | Ionic Silver Metallic
2013 550i xDrive M Sport DHP | Jet Black | Venetian Beige | Dark Red Sycamore
2008 535xi Sport | Jet Black | Cream Beige | Burl Wood