4 months post breast lift with implants, right side isn't dropping and chest feels tight. Will I need a revision?

I'd give it a full 6 months. Discuss with your surgeon. If you were my patient I'd tell you to massage the right breast downward.

It still may drop, but I would suggest wearing your chest band and asking your surgeon to give oral Accolate and external ultrasound treatments to help push the breast along.

Most people have a left breast that sits higher on the chest wall, and then the right. This appears to be the case for you as well based on your preoperative pictures.
Your right breast implant does seem to be sitting high. It might drop slightly with more time, but if you want the implant position corrected, you may need to have your surgeon readjust the pockets.
Augmentation mastopexy is a fairly complex procedure and revision rates are a little higher for this procedure than other plastic surgery operations.
It’s far better to have the implant, sitting a little higher than the opposite, which is implants that bottom out.
Erring on the side of placing the implant low can lead to much more difficult situation, which are far more difficult to correct later.
Follow up with your provider and discuss your concerns with him or her.
Best,
Mats Hagstrom, MD