Will my suit size change after gynecomastia surgery? (Photo)

Made to measure suits, yes. Off the rack, no. The 46R represents shoulder width and arm/body length. If you have had your suits tailored to fit your chest that may need to be taken in a bit. 

 From the photographs I don't think there will be enough change in the circumference of the chest after gynecomastia treatment to make a change in  shirt size or suit size.

It is very unlikely that your jacket size will change after excision gynecomastia, even with the addition of liposuction.  Based on these photographs it appears that your jacket size is being determined by your shoulder width, and the muscularity of your shoulders, arms, back, and chest.