It's a Concept CS, or a CS-based variant (like a 2 door as people have suggested). It could even be the new 7 series for all we know.
I don't know why it woud be a new M6, as some have said. And it sure as hell ain't no F30 3 series concept. That concept rendering is complete BS.
Past: '08 E92 335i|JB|wheels|"eater of HPFPs"
Present:'15 Mustang GT|401A|PP|Recaros|6MT
Sig pic unrelated. I like to go sideways and stuff.