When Punk stole the title from Rocky first thing that popped into my head was Rock is gonna say something like "Punk you can keep it because THIS is the real title" on the next raw.
But seeing as EC is on Sunday what could happen is Rock introduces the new belt design before he starts his match with Punk ala Cena's US spinner against Jesus. I don't think WWE is foolish enough to make everybody glance over the fact Punk took the belt and just gives Rock a replica one.
Judging by the most recent title designs (WWE, ECW, Divas, Tag), people should be more worried that they will change it. Whoever they're using nowadays is awful. It's certainly not Reggie Parks, I know that.
It will never be changed. There have been a few times when they could of changed it in the last year or so, RAW 1000, When CM Punk became the longest reigning champion in the modern era and when The Rock won the title. However I'm guessing they want to keep the design ready for when Cena reclaims the gold and has a lengthy reign.
Plus this title has been one of the longest title designs ever, got a feeling it's going to remain for some years yet.