Rock and the Delay of GI Joe

Hey Scott,
Longtime reader, first time etc.
With the aggressively absurd decision to push back GI Joe: Retaliation to March of 2013 (in order to convert it to 3D, which I can't imagine anyone anticipating the movie could possibly give a frozen s--- about), what does this mean for Rock's Mania availability? He'll likely have to be making the media rounds to promote the film around that timeframe, and promoting the movie is clearly going to take precedent over promoting Mania, even if he's in a marquee match up. So is Rock off the table? Will he even be able to do Mania at all, with his schedule?
I know Rock vowed to be back for Mania season in 2013, but that was obviously before this fitfully ridiculous corporate decision. So will Rock still do Mania? And if not, what could WWE start building right this moment to make up for it? I would imagine building up Brock as an animal for Cena to finally defeat for the title in the main event would be off the table, since Cena's already won. Maybe put Brock against the Streak? Or Cena against the Streak?
I imagine the commentariat will be infinitely more clever about this than I am.
Keep up the good work,

I'm pretty sure that "conversion to 3D" is code for something else, like "reshooting all the crappy CGI" or "trying to edit the movie into something halfway coherent."  
That being said, it's a pretty easy 2-for-1 deal for WWE and Rock.  When he's booked on shows to promote Joe, he can be all "by the way, I'm also doing Wrestlemania".  And when he's on RAW leading up to Wrestlemania, they can plug the s--- out of GI Joe.  SYNERGY.  It'll be fine, no replacement match needed.  
Brock against the Streak would be pretty interesting, especially if Brock works that new style against Undertaker.  I can see Undertaker wanting to try an actual MMA type match.