Does nipple rings prevent you from breast feeding, if you decide to have kids in the future?

Can cause problems ! Nipple Piercings have led to cellulitis & abscesses. The jewelry can snag against clothing with potential of traumatic tears to the nipple. Additionally, scar tissue on the nipple or jewelry can block a milk duck & in some cases make it more difficult to latch during breastfeeding.
Probably not. Nipple rings can destroy some of the ducts, so they may not be able to let some of the milk flow out. This can be painful for a few days as the glands build up milk and then have to resorb it. The remaining functional glands will make up the slack, though.