If the WWE does do this, why use Cena for that segment when using HBK makes 100 times more sense? HBK will be there for his HOF induction, having him come out would blow the roof off that place, and he is closer to HHH than Cena will ever be.Here is my scenario...
Sheamus isn't participating in any match at WM. he storms the ring, and demands a match. He has an open challenge which Cena comes out as if he will wrestle him. Gives his five minute promo. Then tells him he found a person for him
As for the OPs question, his return has been rumored for the last 3 months and he still isnt back. The only people that truly know the answer are creative.