If regularized, the SS commissioned officer can go up as high as any regular commissioned officer. Some OTS (which was also an SSC scheme) officers made it to the General rank (Gen Khalid Mehmood Arif, VCoAS comes to mind among others.) There are quite a few others of the rank of Maj Gen as well.
In the old days the SSC was a scheme used to make up for the shortage of officers in the three services (and specifically in the Army). Over the years, the SSC scheme has been used to bring specialized educational backgrounds into the Services. Give them abbreviated training and then commission.