Rivet, I doubt they will push mma at all. They had Chael in the audience recently and never acknowledged him. If any show up just to support Brock, they probably won't acknowledge them. I also think Vince would like for people to forget Brock's mma career considering the last couple fights he had that ended it... They have a way of erasing (ignoring) history in the wwe. I think Vince is smart enough to realize mma hurts prowrestling in a big way and has taken a lot of the fans who want to see real fights rather than rehearsed, whether he admits it or not. I think he would be smart to try and recruit Tito or Randy Coture in some fashion like he did with Dan Severn and Ken Shamrock back in the day. I can see Tito and Randy transitioning well like Ken did. Ken actually did pretty well.
For Mania, an awesome ending would be... Rock/Cena - ref is down, HBK comes out (already a ref that night) kicks Rock, counts Cena as the winner. (sets up hbk rock next year). Then just as you think the show's over and cena is celebrating, here comes the pain. Brock F5's Cena. Setting up the main event for next year.
I think WWE knows they did a great job by building the main event for a year with rock/cena and they will do the same this year on a bigger scale. I wouldn't get any hopes up though, I always expect them to drop the ball and I'm rarely disappointed.