Please don't be unhappy yet! Your body is just barely beginning to heal, let alone rebuild your deltoid muscle to take over for the no-longer-used rotator cuff.
During PT you will have the opportunity to work on developing the deltoid, but don't rush things. Full recovery takes time and over time you should see improvement.
When you begin PT, be sure to let the therapist know you want to work on minimizing the difference in appearance of your shoulder so they can help design the right exercise program for you.