This GIF just adds more to my suspicion that it is Abraham that gets it.
Its all about proportion. Glens head is way too large in proportion to Negan, so it is not Glen. Comparing those two pictures, Negan is just far enough back to be aligned in the position of Abraham.
Writers, producers and directors like to add metaphors to shows, and there is a scene in that last episode where Abraham is driving the RV, and seems very happy and content asking Sasha what she thought about the possibility of them having a baby. The sun is setting in the background behind Abraham. Shining through the trees and casting a glow onto him. This, in my opinion, is the "end of the road" for him.
Yes, the show has planted some seeds to try and throw you off.... Bad guy telling Rick that it might be his last day, Eugene handing over the plans for making bullets, but Its Abraham that is going to get it.
This is my theory. I will even put money on it.