I am not convinced that this is the 4 just yet.
South said this:
Which I take to mean that the picture is of a production vehicle (more advanced than an FEP), not of a concept (less advanced than an FEP, as least as far as product evolution goes). There's no way BMW would show us the production car when they are about to unveil a concept. Note that I am not saying it couldn't be the 4 concept (I may be misinterpreting south's words), just that it does not seem certain to me quite yet.
Also, LA comes before Detroit. What might BMW be unveiling there, and could this be it?