Heres what I think should happen (if I was in charge of booking) in the next few months...
At Summerslam, Punk defeats Cena to become Undisputed WWE Champion following a highly competitive match akin to their superior bout at MITB. Cena will offer a handshake following the match and just before Punk gets a chance to shake his hand, Alberto Del Rio's music hits and he comes out with the MITB briefcase. This gives us a what if? scenario for all we know Cena could have given Punk the AA or Punk could have given Cena the GTS during the handshake, but instead Del Rio hits the ring and both men throw him back out.
On the RAW following Summerslam, Cena and Miz pin each other (or some screwy finish) in the number 1 contenders match for Night Of Champions. Therefore the match becomes a triple threat. Also on RAW, Del Rio announces his intention to cash in later on after Punk has his first defence against whomever. Following the match where Punk retains, Del Rio comes out with the MITB briefcase, only to be stopped by both Cena and Miz who come out to the ring and Punk, Cena and Miz all have a small brawl that ends with Punk standing tall.
At Night Of Champions, the triple threat match would go ahead as planned and following some stunt that takes all three men out, Del Rio comes out quickly to the ring without his entrance music. Del Rio covers Punk and the referee counts the three, Del Rio then makes a swift exit with the WWE Championship. The next night on Raw, Triple H will scold all three men and declare that the number 1 contenders spot is up for grabs elsewhere, Rey Mysterio will win the number 1 contenders spot and will feud with Alberto del Rio during WWE's tour of Mexico. Meanwhile, Punk, Cena and Miz will continue to feud with Cena acting as the classic face, Punk as the Austin type face and Miz as the heel. At Survivor Series either Del Rio will retain (depending how his run has gone as champion) or someone else will win the title.
By Royal Rumble (Elimination Chamber at the latest), Cena will have regained the WWE Championship in time for his match against The Rock at Wrestlemania.
ETA: The Royal Rumble is a difficult one, since its pretty much a lock that Cena will be going to Wrestlemania as WWE Champion, it means that the winner of the RR match must be a Smackdown superstar. Daniel Bryan has already voice his intention to cash in at Wrestlemania, so for that reason I reckon the WHC match at Wrestlemania will be a triple threat, featuring Daniel Bryan, the WHC and the RR winner.