From what we've seen for the build-up for SummerSlam, I believe this occasionally-unpredicatble pay-per-view will see two possible outcomes, as it pertains to both the WWE Championship and World Heavyweight Championship matches.
With the Rhodes/Sandow rivalry being a somewhat main attraction for the upcoming pay-per-view, and it revolving round Sandow's prized Money in the Bank briefcase, here is an outcome to consider that could change the World Title picture:
The Christian/Del Rio World Title match hasn't been THAT much of a build-up, and despite the Title not being on the line, we have seen on SmackDown this past week that the WWE has given us one of the SummerSlam main events away for free, as Christian defeated Del Rio in a match.
Now, I believe the first match of SummerSlam will be Christian taking on Del Rio for the World Championship. (On a side note, I DON'T believe Ricardo Rodriguez will be involved in the match since he is being punished by WWE for his wellness policy violation, and will sell the beating from Alberto from Raw). Christian will win the World Heavyweight Championship in the opening match, only for Damien Sandow to cash in his Money in the Bank briefcase and win the World Heavyweight Championship (The Shield may attack Christian, leaving Christian vulnerable for Sandow to take advantage).
A backstage segment will then occur, probably involving Triple H, the McMahon Family or one of the General Managers. Damien, who is yet to face Cody Rhodes later on the card, will be forced/convinced to defend his Title against Cody Rhodes later. Due to interference from both Christian and Del Rio, Cody will DEFEAT Damien and become the brand new World Heavyweight Champion...leading to Cody defending the Title against Sandow, Del Rio and Christian in a Fatal-Four Way Match at the next WWE pay-per-view.
Another scenario, involving the McMahon Family struggle, that involves both Heavyweight Championships could play-out like this:
We all know that Triple H and Mr. McMahon are at war just now in WWE, and Vince has promised to be involved in the WWE Title at SummerSlam in some capacity. A confrontation between HHH and Vince has been building towards SummerSlam as much as the matches have been. So, at SummerSlam, what if, again, Christian defeats Del Rio for the World Heavyweight Championship and it's Mr. McMahon that leads Sandow to cash in and win the World Championship! Later, an angry Triple H promises that Mr. McMahon WON'T mess with the WWE Title match between Daniel Bryan and John Cena.
Later, with Triple H AND Mr. McMahon at ringside, Daniel Bryan takes on John Cena for the WWE Championship. Near the end of this epic match-up, Ryback attacks! Ryback, who has had problems recently with both men, lays out Bryan and Cena with a DOUBLE shell-shock!! Triple H, believing Vince sent Ryback, attacks Ryback and takes him out of the ring. As both Bryan and Cena are down, Bryan slowly makes the cover and pins Cena to become the BRAND NEW WWE Champion!
Randy Orton appears and comes down to the ring and cashes in the Money in the Bank briefcase. Orton hits an RKO on Bryan and pins him to win the WWE Championship! But Triple H confronts "The Viper" as he is upset at the way he won the Title. Out of nowhere - and to everyone's shock - Orton drops HHH with an RKO. Mr. McMahon slowly enters the ring and raises Orton's hand (turning him heel in the process). Afterwards, Orton goes to punt Triple H in the skull, at the approval of Mr. McMahon. But Stephanie comes out and begs him not to! John Cena stops Orton in his tracks, but Ryback returns and takes out Cena again. Orton then hits an angry and recovered Daniel Bryan with another RKO. As Mr. McMahon and Orton smirk as they stand over a fallen "Game", Mr. McMahon tells a downed Triple H, "You're winner and NEW WWE Champion, "The Viper" Randy Orton!"
As a 'SCREW YOU, THIS IS MY COMPANY' to Triple H, Vince will have been responsible for crowning both new World Heayweight and WWE Champion's in Damien Sandow and Randy Orton (heel), respectively. This would also have Ryback, on Mr. McMahon's side (because McMahon believes Ryback is what a WWE Superstar SHOULD look like) be at the centre of a feud with Triple H.
SummerSlam closes as Stephanie, from the ramp, looks on in shock and awe!