How will location of nipples change as implants drop?

Saline implants are designed to be overfilled, and most of us do to avoid decrease the risk of ripples. You now have larger implants and your tissue may need to stretch some to accommodate them. Once settled, your nipples should be in good position if they were before surgery. Please discuss any concerns you have with your surgeon.

Dear NoShameInBeingVain,
dropping of implants is part of the healing process and this occurs after the tissues surrounding the implants slowly relax, allowing the implants to settle into their final position. It can take about four to six months for the implant to drop down to their final position.I understand that you are worried about your implants are not dropping as expected. However, you are still in the early phase of the recovery period. Please do allow some time for the healing process to occur. If after six months, you are not satisfied with the appearance of your breast, you can visit your plastic surgeon and discuss your concerns.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

This is a good question that is very common.
To answer your first question, saline implants are often overfilled intentionally as this helps prevent the implant from rupturing, and prevents the implant from wrinkling (rippling effect). If the implant is under filled or filled to the limit, the risk of rippling is higher.
The final position of your breasts after implant placement will take up to 2-3 months. Over time, the implants will drop and the position of your nipples in relation to your breasts will change, including the angles of your nipples. If you are happy with the position of your nipples immediately after surgery you will be unhappy in 2-3 months; if you are unhappy with with the position of your nipples now then you will likely be happy in 2-3 months when they drop. Sometimes wearing a band in the upper part of your breast and breast massages (I generally recommend starting massage at 2 weeks after surgery) can help with (and accelerate) the process of implants dropping over time. It is important to talk to your plastic surgeon to discuss this to see if this is something safe and feasible for you, depending how far after surgery you are.