Punk's last heel turn was a slow burn that took at least a month too. I see no problem with it. In fact, I think this is how turns should be done most of the time.
the point of the story is punk knows he almost lost to cena, he will manipulate everything so he doesnt have to face cena again
at summerfest they cant repeat the booking of last week in a dq and they cant have punk beating cena clean, show being involved is the only logical answer but i agree cena will be involved too