I mean other than the actual issue and the ENDING and the characterization of the Red Hood; there's the wall evidence, Morrison saying Jason was going to show up in B&R #4; and I think in an interview somewhere he said Philip Tan was going to draw Jason. (At least that's what I read... somewhere. My memory of source is alluding me right now...)
If it's not Jason, I will eat my words in a bowl of soup. ;-P