The appearance of breast implants when your 50, 60, or 70+ years old is highly correlated with how your breasts will appear when your 50, 60, or 70.
No one can necessarily predict how your breasts will appear as a result of menopausal changes.
This comes down to fortune telling and is similar to asking how your belly will look when you have children. No one can predict whether you will or will not have stretch marks.
Having said that I can generally say that women with very small breasts who undergo augmentation with a relatively small implant (270 and less) tend to show only mild changes with aging in contrast to larger breasts with large implants.