For women with moderate to severe breast sag or asymmetry, a breast lift (mastopexy) may be recommended to ensure the best result and longest lasting result. Failing to have a breast lift when necessary will only lead to a less than ideal result leaving the patient unhappy and needing a revision surgery. A larger breast implant can help lift the breast, but the low hanging breast tissue will still be present causing a disconnect between the implant and breast tissue located at the bottom of the breast. This is one issue that must be discussed with your surgeon in order to maintain shape and placement after augmentation. I wish you the best, and hopefully you will be able to have it corrected easily.
From your photographs, it's my opinion that your plastic surgeon did an excellent job producing pretty good symmetry given what the starting point was. To me as a plastic surgeon, the upper pole looks pretty full both in the front and side views. Should you wanted to be more abrupt, like a push-up bra would give you, there are essentially two options. I've had good success in the past few years with fat grafting of the upper pole. Alternatively an ultra high profile implant, that has the same base width of what you have now, may give you that look for a while. As the skin stretches under gravity, the upper pole fullness may slightly decrease over time. Best of luck.
Overall, given your pre-existing breast asymmetry, I think that your plastic surgeon has done a very nice job for you. Based on this assessment, I would suggest that you avoid further surgery unless you are very unhappy with concerns such as projection and/or "upper pole volume". If this is the case, then revisionary breast surgery using larger and/or or projecting breast implants will be necessary.
Again, important to remember that absolute breast symmetry will never be achieved and that every operation carries additional potential risks/complications. In other works: make your decisions very carefully, after careful consideration of pros/cons/risks/complications associated with all options.
I hope this helps.