Here's some interesting analysis about why the WWE would want to unify the titles:
"If WWE unifies the two titles, they also don't have to worry about having to build up two challengers at once, especially with the slim pickings they have right now:
•They clearly don't want Daniel Bryan or Damien Sandow in main events.
•Del Rio and Ryback are done after being dispatched so convincingly by Cena.
•CM Punk is biding his time in midcard feuds until he's put back on the road to another title reign.
•Big Show just got punted, and they'd be fools to rematch him with Orton.
•Dolph Ziggler is in purgatory.
•Christian might as well not even be in the company with how easily he gets seriously injured nowadays.
•Sure, Rey Mysterio is back, but, uh, see Christian."http://bleacherreport.com/articles/1864402-wwe-survivor-series-2013-wwe-is-smart-to-start-randy-orton-vs-john-cena-feud