Cena won't turn heel until he stops being hugely profitable. I think the flaw is that the WWE is not taking a serious enough approach to building up someone who could push merchandise just as well.
Cena going over Rock makes sense, but there's no chance in hell I would guarantee it. Nor would I make it the most likely scenario, honestly. There's plenty of reasons why Rock would go over in this situation. Especially if it ends up being THE final match of the night.
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TheRock ~ Slow dramatic zoom-pan. Doesn't phase the hooded man.