The issue on Rock/Cena II happening:

The issue with Rock/Cena II isn't this match, per se. The things that you said about Wrestlemania needing a sequel, this year, to Cena/Rock is right. However, the real problem isn't in Cena/Rock getting a sequel [just due to it being a hundred million dollar match for casual buyers] Cena/Rock II itself is a finish to the trilogy of 27 [Rock's return, the way Miz/Cena went] and 28 [Cena/Rock I- Rock wins.]  The only problem right now is that the argument for "why" Rock/Cena II needs a sequel, in itself, is the real problem when it goes further. 

We've seen in the current Hollywood format the same point: When a non-licensed movie [think, "The Hangover", "Paranormal Activity", "Saw"] becomes a breakout hit movie- the current era of sequels is to- instead of reinventing the wheel and giving people something different, merely rewrite the same movie that was already a hit and send it out to theaters. 

This goes into the REAL problem with Cena/Rock II: How much of Cena/Rock is TOO much? The old claim for Wilt Chamberlain in basketball went with the logical problem- If you have a player who shoots 50% from the field, then by logic he should shoot more. And, going further from there, why should anyone else on your team ever shoot the ball? Having Cena/Rock II, this year, is the right decision- but the argument you've given makes another problem- if the match goes for once-a-year casual buyers, then by definition, should Rock and Cena merely wrestle each other every year until one of the two dies? There is a good thing for Cena/Rock II, happening at Wrestlemania 29, but if we're getting Rock/Cena: Eleven Times In A Lifetime at Wrestlemania 39, there's a problem.

They've only had one match. EVER.  This isn't anywhere near burnout yet.  And if one match draws $100 million over and over, why not keep doing it until it doesn't?