The distance between the breasts after surgery is determined in part by the distance between the breasts before the surgery. Typically, breast implants are placed below the pectorais major muscle which is behind the breast. This muscle attaches to the breastbone abd those attachments are usually left alone at the time of surgery. I always try to get the implants as close together as possible but you want to mostly leave these muscle attachments alone because releasing them too much can cause visibility of the implant edge. In this area that may be visible in some clothing or a bathing suit.
Certain bras will accentuate your cleavage more than others. More volume in this area will allow more cleavage in certain clothing. The gap will not be any greater than it is now. The size implant that is ideal for you is up to your plastic surgeon after he or she discusses your goals and after examining you.
Thank you for your question and for the photo.