Reason I think its glenn is because:-Next few stuff are about maggie
-Hits out at rick
maggie spoil-v
-maggie pregnant still -builds storymore than abraham(everyone would be more alright with that even if he's gd character)
-RK said that there was signs within last few episodes that will tell us who it is (Stuff like Glenn actually looking at lots of pics of negan lucille kills.
Abraham prediction-v