I really wouldn't want Sheamus as the face. I dislike the Irish accent, the over use of the word "fella" and his random blabbering. If Cena retires at 40, I expect Orton to be the transitional top dog till they build someone up. No one knows who'll be next they may not be on TV or hired yet.
Someone could randomly just burst out at anytime really. Like Cena when he accepted Angle's challenge who said whilst watching it "this guy is the new face and gonna be huge"? For me he had the second coming of Maven all over him. Proved me wrong.