Is it confirmed that The Rock's going to be at Summerslam? I remember reading that he'll be at the big PPVs after Wrestlemania.
Probably won't be confirmed until somebody starts calling him out during the summer, but with Summerslam being in LA again this year I kind of expect him to be there.
If Cena turns at Mania (looking doubtful now IMO but lets roll with it), since Rock is doing Raw the next night and then disappearing for a few months to film two more movies, it wouldn't shock me at all to see him come out on Raw and lay the groundwork for the rematch at Summerslam. Obviously they've booked it well in advance before, wouldn't be surprised if they did it again.
That would give Summerslam a HUGE main event already and if WWE wanted to, they could go through the summer again with Punk vs. Cena for the WWE Championship but this time it's face Punk vs. Heel Cena so it's fresh. From there, you'd expect Cena to go into Summerslam with the championship so it's Rock vs. Cena for the title, but with more of a face/heel divide this time around as well.