This should be a plugin since you cannot have it default in the program, i always rotate images and forget to save, i think most people rotate images when the camera didn't properly detect that the image is on it's site i usually have around 5-10% of my photos in the incorrect side and have to rotate and (CTRL+S) them all the time, plus people expect that when they rotate an image the computer "remembers" that they rotated it the next day. :).

a time delay would be nice like 2 secs for when like rotating clockwise twice. or even when eog exits (either from that image or the program itself)