Styles/Balor has been confirmed by WWE since yesterday.
I'm curious if we hear whether they inquired about Cena's availability/willingness to take Roman's place.
I doubt they even considered it because while Cena is still a big draw he wouldn't have been seen as something special enough to take away the anger at losing The Shield reunion in the main event. They had to do something BIG that would keep people who bought tickets from wanting refunds or being pissed off and shitting on the show in a GAB 91 type scenario. Angle was probably the one person they had readily available who fit that (no Matt Hardy does not fit that)