After the Australia incident, I'm not sure Punk has a near/long-term future with the company. I have the feeling that the Powers will try to put as much distance between themselves and Punk as possible. Will he walk out as champ? Depends on if he even makes it into the match.
IF, Punk does make the match, I see something like this happening.
Before the match, VKM struts out to the announce desk, kicks Cole to the curb and it's Vince and Ross, just like the early days long past. King as well.
Match starts, some nice back-and-forth, then Punk get's the upper hand for the better part of the match. Super-Cena makes his appearance and Vince leaves the desk and get's Cena's attention (not interfering) and Punk get's the upper hand again. VKM screams at Punk to punish Cena for extortion (getting Punk back in the ME). Punk finishes with the GTS, wins the belt, Vince jumps in the ring and before he can utter "You're Fiiiiiiiiired"
Del Rio runs into the ring, MITB case in hand, yelling to the ref. Hits Punk with the Arm Bar and wins the WWE Championship title.
Monday on RAW, Vince announces that even though Punk didn't walk out of the company as champ, Cena is still going to face the consequences of crossing the boss and get's suspended indefinitely.
Is it all predictable? Hell yes, but that's what the company has been doing for years now. But it keeps the title belt in the company (what VKM wants), Punk get's to leave (what he wants), Cena is off TV for a couple of months (what most fans want) and there's a new champ with nearly unlimited options for new feuds (what all the fans want!).