According to Subaru's release, "In the future, further models tuned by STI will be available in the US.
These cars could feature more extensive modifications from the factory
than previously offered, such as suspension, performance, braking,
chassis and aerodynamic upgrades."
Subaru has already started spreading its STI-engineered parts, which replacing Subaru Performance Tuning (SPT) aftermarket parts in the US market. Plans for fully tuned STI vehicles have not been announced.