There are a few possibilities that would explain why Subaru is testing the BRZ with these new components. The first possibility is that Subaru will sell these aero parts as optional accessories for the standard BRZ model, giving customers something to make their cars look that much sportier. Alternatively, it is possible that Subaru is working on a tS variant of the car, as it did with the previous-generation BRZ. Indeed, the black winglets of this prototype are very similar to those featured on the old BRZ tS.
The final possibility is that we are looking at an early prototype of a full-blown BRZ STI model but unfortunately, we think that is very unlikely.