Interesting question, where does the Miz go from here?
The Rock? No. Rock should not be thrown into the title picture. The Rock is still The Great One, but now that WrestleMania is finished, there's no reason to put the Rock in the title picture.
Cena/Rock? See above.
Morrison? This would be the ideal feud to lead into Extreme Rules. Morrison's Parkour style fits the PPV theme perfectly, and the spots that he and Miz could perform can definitely steal the show and elevate Morrison. Morrison also seems to step up his mic work and promo skills when he's involved with The Miz. These two definitely have chemistry together, and this feud can definitely be entertaining. Morrison's #1 Contendership was ruined by giving him his title shot right away instead of at the Royal Rumble, and I'd love to see how Morrison could handle main eventing a PPV.
Ziggler? No. While Ziggler's a former World Heavyweight Champion, I see absolutely no interest from the crowd in DZ unless Vickie Guerrero is there to scream and wail at ringside. The crowd just doesn't care, even with DZ being shoved down our throats. Is Ziggler a good wrestler, talented, and fun to watch in the ring? Of course! Just look at the Ziggler/Bryan match from last year's Bragging Rights and you'll see an overlooked gem that could easily have won Match of the Year (had it not been for Taker/HBK II).
Orton? I hope not. Orton and Miz are about as entertaining to watch feud as Lawler and Miz...not very entertaining at all.
Punk? No no no! While Punk is a great wrestler and entertainer, I do not believe that Miz/Punk have the skills to pull off a heel vs. heel story. This type of matchup is very rarely used for good reason. And turning Punk or Miz face would be a HUGE disaster.
Bryan? Although the Miz did wonders for Daniel Bryan while the two feuded over the United States Championship last year, I don't see Daniel Bryan as being ready for the main event at a PPV quite yet. If Bryan and Sheamus were disrespected enough last night by having their title match not only thrown out, but changed to a Battle Royal, while The Corre remained on the card for a squash, I don't see management giving Bryan a shot at a main event.
Sheamus? See above with Punk and Bryan.
Kofi? While Kofi could shine in a match at Extreme Rules due to his style (see Morrison), I just don't see Kofi as a legitimate contender yet. Mainly because creative ruined his shot when they buried him during the Orton/Kofi feud. That feud had potential! That feud showed a new, serious, and badass side of Kofi that got buried...if he could return to that fiery persona, he'd have a great shot.
Big Show? Interesting idea. Former Tag Team partners in ShowMiz, they never really got a decent break-up feud once Big Show left for SmackDown. Big Show knocked out The Miz with a punch, big deal. They could write a decent feud for the two of them, and it'd be interesting to see Miz really tested against a giant, and elevate his devious heel persona. But I'm not quite sold on the idea.
Quite simply, I would say to give John Morrison the next shot. There's so much history between the two, they have great chemistry, feed off each other, and can work in the ring together well. Take the chance and let them shine!
