After watching RAW again I had to keep watching one promo. The part where the Zookeeper tells Cena that he and the rest of the WWE locker room are worried Cena is going to follow Wade's orders and take them out followed by his recommendation to quit could be where they start the heel turn for Cena. Maybe for a few weeks guys come up and say he's not bigger than the rest of the locker room and he should just quit, then eventually Cena sees that he needs to go back to Thuganomics and taking everyone out. Is it likely? No, but it seems like a logical way to turn him heel to me.