Apple's iPhone "S" models tend to be about refinement, and if a report by 9to5Mac proves correct, the presumably in-the-pipeline iPhone 6S and 6S Plus will be getting some attention in the camera department as part of their mid-cycle refresh.
The site's sources say the cameras in these phones will get a bump from eight megapixels to 12MP, along with an improved image signal processor that's supposed to counteract any negative side effects of the increase in pixel density (usually noisier images, from my experience).
The beefed-up ISP could make for an upgrade on the video recording front, too. 9to5Mac's sources think that Apple will add 4K video recording to the iPhone 6S and 6S Plus, making them the first iPhones able to record at that resolution. For selfie-takers, the front camera is also supposed to be improved, though the exact changes in the works for it are unclear. We'll have to see if these changes play out if and when Apple takes the wraps off the new iPhones as it traditionally does in September.