The crowd won't make a difference since Rock and Cena most likely won't even be able to hear them. It would be dumb to have the Rock win since he is leaving after Wrestlemania.
There is the thing, it is NOT confirmed that the Rock is leaving after WrestleMania, it's simply expected. If you guys remember in 2011, the Rock could have participated in Extreme Rules, he didn't. Chances are, he won't again. I'm hoping that it's a triple threat and the Rock wins again. Chances are he won't, but lets just take a moment to analyze this here:
His Movie Premieres - Obviously expecting a lot of travelling from him. But all of those five movies coming out this year from him or such will be out by the end of July. Let's see the gap between the premieres: GI Joe comes out at the end of March and so is supposed to be advertised alongside WrestleMania in NYCity. Two months after that comes along Fast and Furious 6, which is well past Extreme Rules. Since premieres are about two weeks, at most we would have the Rock missing two shows in between WrestleMania and Extreme Rules, which implies he could attend both events. It does hinder events past Extreme Rules, which means Over the Limit and Money in the Bank.
His TV Show - I am well of aware of this "hero" show that was just announced, but the thing is that since this was just announced it is probably going to get into official set development by April as pre-prouduction development and planning is likely happening right now. So we can expect the show to start filming as soon as late April and as late as late May/early June. This does not count him out of Extreme Rules, though it does destroy Over the Limit.
Hercules - Obviously this movie may be the main reason people are saying the Rock will not be attending Extreme Rules. But the fact of the matter is that this movie was in talks to get approved for so long things like production, scripting/screenwriting are just starting now and won't be finished for about three months, after which principal photography and such. A film set in Greece about wars would also want the best weather, so you can expect August for the actual filming to start. This hinders Summerslam but not Extreme Rules and Over the Limit.
That is the Rock's schedule, I won't count him out of Extreme Rules, but anything after that, I would definately count him out of. Vince knows what is best for business and if he can get the Rock for Extreme Rules it would be great for business. I mean, while I personally am happy that there is a slim chance that the Rock can stay for at least one more event, I know Vince is exited. It builds up several Austin Aries and Steve Austin like stories for Vince, Cena going on a face-rampage through the year and even changing his character. When W30, Rocky comes back and they have a Rock-Austin III feud with Cena angered that he just cannot beat the Rock. I am opposed to that feud, but as I have said, Vince does what is best for business and there IS a slim chance that the Rock might stay.