Although we (Bimmerpost) believe this to be an F30 3-series in testing, Autocar claims that this is a disguised F30 3-series sitting on top of the upcoming 3-series GT's mechanicals. According to them:
Underneath this disguised 3-series are the mechanicals of the forthcoming 3-series GT. BMW hopes the new model will broaden the appeal of the 3-series in the same way that a hatchback variant has widened the scope of the 5-series.
However, the new car won’t just be a smaller version of the Five GT. This time BMW is aiming to produce a fastback 3-series rather than the business express limo that is the Five GT. The 3-series GT will be more of a rival to Audi’s A5 Sportback, which is halfway between a fastback A4 and a four-door A5.
Originally Posted by SCOTT27
I can see where they think it could be a GT just by observation.
The wheels being used on this prototype are new Y-Spokes designed for the next X3 and if you look at the ratio from the road to wheelarches you can see extra clearance in the arches and from the road height.
This gives you some clues that this is no ordinary 3er sedan.
Although the 3er Gran Turismo will not be based upon the 5er and offering the same amount of luxury and space it will be a more compact alternative to a SAV or Touring. In the near future BMW will revisit it's Progressive Activity series with a Concept showing the direction of the new car.
Interestingly enough is that before Christmas BMW have asked for an update on a similar sister model a five door Coupe to move into a design competition. This model is a five door fastback variant of the Shooting brake interpretation of the chosen concept. We have always discussed the intervention of a 4er model again based on the modular matrix of the upcoming 1er and 3er , both cars where BMW can make good profit from.
If the idea goes ahead and nothing is final but only in discussion, then the 3er Gran Turismo could be called the BMW 4er Gran Turismo and the fastback known as CS 4.