I had a partial tear to rotator cuff. Opted for physical therapy rather than surgery. After several weeks of therapy still some stiffness. Will the stiffness ever go away?

Yes. Partial rotator cuff tears are often treatable with therapy, but may take 6-12 weeks to improve. Oral and/or injectable steroids are helpful and may speed recovery. If non-operative treatment fails, arthroscopic surgery works quite well. The inflamed bursa and partial rotator cuff tear will be debrided. Bone spurs are also removed. The typical recovery is 3-4 months.
It should. It is perfectly reasonable to try to rehabilitate a partial-thickness rotator cuff tear. However, it is likely that you will need more than a few weeks of therapy for the stiffness to resolve. If the stiffness persists or if your pain returns despite a few months of therapy, you may need to revisit the idea of surgery.
Likely. Most patients with a partial tear of the rotator cuff improve greatly from pt, anti-inflammatory medication, and an occasional steroid injection. If the stiffness is not improving, a frozen shoulder may have developed or the tear may have progressed depending on the physical exam. See an orthopaedic surgeon for an evaluation to help determine if progress is taking place.
Yes and no. It is possible that your shoulder will loosen up with continued pt. Having surgery does not guarantee full rom. Often times people remain tight after surgery for months and months. If your pain is improved and function is very good then stick with nonpperative treatment. If you have plateaud and are frustrated think about surgery and talk to your surgeon. Thanks.
Stiffness. The stiffness in the shoulder may be related to an onset of capsulitis or frozen shoulder. Therapy should be directed to scapular and glenohumeral mobilizations and glides; a NSAID may be helpful and perhaps if the condition worsens or plateaus an ultrasound directed cortisone injection.