My s6 is sent in for a battery replacement under my apple care. I’m curious if anyone has sent in their s6 for battery replacement? I have a Nike s6 LTE and have heard sometimes apple will send a new model back to you (s8). Is this true?
No, they will send you a refurbished device the same spec as the one you sent, typically. There would be isolated cases whether they have to send people out something newer but that's by no means typical.
It’s happened in the past, I seem to remember some series being low in stock so a lot of people got the next one up… series 2>3 maybe, or 4>5? But like @Howard2k said it’s not typical, and it’s not controllable. It’s highly unlikely you’ll get anything but a replacement S6.