I've had polymyalgia for 1 year. Am on pednisone 5 mg daily. What would happen if I stopped taking the meds?

Depends. Maybe nothing. Maybe it would come back. Usually, i keep tapering my patient's dose down until they are able to come off the Prednisone completely. If you've been on 5mg for a year, you probably want to slowly decrease it under your dr.'s supervision to avoid adrenal insufficiency.
Depends. If you are on Prednisone you should not just stop it. You need to work with your doctor on managing your dose. It needs to be decreased slowly based on your clinical symptoms and response to dose reduction. You should talk to your doctor before changing your dosage.