OK, the answer is yes.
No system to convert Sonic drums to aftermarket discs exists.
A big brake conversion (such as Brembo's) will improve braking. There are other less costly methods available today to improve braking.
When the RS is available, the rear disc brake system should be available.
Unless racing/autocrossing the only reason to change drums for discs is aesthetics, in my humble and uninformed opinion.
Laborsmith