Necrosis after tummy tuck and PS doing nothing. What can I do about it? (Photo)

Sorry to see that you're having this complication. Unfortunately skin loss and wound healing complications are a risk with tummy tuck surgery. Because it has been only three weeks, I think your surgeons advice is good. It is typically best to allow the body to heal as much as possible prior to debridement. This will allow the necrotic areas is to "declare" themselves. A more focused debridement can then be performed. Skin and underlying tissue that is obviously necrotic or infected needs to be surgically removed to facilitate healing, however it does not appear that you're at that point based on your pictures. Of course it is difficult to make this determination without a physical examination. Your recovery will now be lengthened, however you will get through this and heal adequately over time. Try to maintain a positive attitude. Best wishes.

Keep listening to your plastic surgeon.  It seems that you are improving with conservative treatment.  That is the best thing to do at this time.  There are many wound care options to choose.  Seems you are on the right track.  I agree with Dr Pousti that you most likely will need additional surgery in the future.