Subaru doesn't seem to be interested in filling the gap for a more powerful, turbocharged BRZ coupe. But according to Car&Driver magazine, Subaru is working on a special edition version of the BRZ featuring primarily cosmetic add-ons including "special side skirts and a rear wing as part of the package".
The special edition BRZ won't get any of the STI-branded chassis bits to improve handling though.
[JDM Subaru BRZ tS and tS GT pictured]