I know HHH has an ego. Any successful person in any walk of life has to have some kind of ego and HHH has been very successful in the professional wrestling business. Therefore, he has an ego.
I also know that Vince wanted HHH to win at Summerslam. Vince, as he's gotten older, has gotten much worse about proving that he's right about everything. It started 10 years ago when he crushed the guys who came over from WCW when he bought the company. Rather than allowing them to be booked as legitimate threats, he destroyed their credibility. Christian left for TNA, became NWA Champion, and came back. Vince made it clear he never thought Christian could be a main-eventer and it took Edge's early retirement to basically force Vince to put the WHC on Christian. Lesnar did basically the same thing, leaving for the NFL and then UFC. Now he's back, so let's pay him a lot of money, build up his heat, show everybody how much of a badass he is, then have him face Cena. If Lesnar crushes Cena, the whole storyline makes sense. But, Vince decided that the "Face of the WWE" can't lose to Brock Lesnar, so Cena goes over him after being dominated the whole match. Even people who don't follow the WWE thought it was a stupid ending to that match.
HHH has a head for the business. He doesn't mind standing up to Vince (why else do you think he was the one chosen to tell Vince he was "fired" by the Board on the air; others were most likely too afraid even to do that in a kayfabe capacity). He knows it's stupid to have Lesnar lose to him twice. It wouldn't surprise me to find out that HHH doesn't really want to do a comeback angle and beat Lesnar at Survivor Series. Whether or not Vince will allow the victory of Lesnar over HHH to be the last image people have of the feud has yet to be seen, although the more it's talked about, the more likely it is that HHH comes back for one more match at Survivor Series. Then, we'll just have to see how it goes, but it does make sense for the good guy to come back to beat the bad guy. After all, that's basic story structure and actually does make sense from a plot design perspective.
What makes more sense (to me, at least) would be for HHH to back some young guy (maybe Ryback) and be in his corner at Survivor Series. Then let the young guy (with his mentor HHH) beat Lesnar (with his sniveling spokesman Paul Heyman) at Survivor Series. That gives Ryback (or whoever they chose to fill that spot, Ryback just makes the most sense to me) a hell of a rub for having beaten Lesnar at one of the big 4 PPV's.
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