While it remains to be seen who will be the champion for the match, it appears that John Cena dropping the WWE Title at SummerSlam, or the night after, is very likely. With the constant teases that Orton will be cashing in at SummerSlam on Sunday, that appears highly unlikely at this point. They may do an angle at the PPV where it'll look like he's about to cash-in but it won't end up happening. The current word is Daniel Bryan will wind up leaving SummerSlam with the title. The feud with Randy Orton will begin shortly thereafter, likely on RAW.
As noted earlier, Cena will be taking time off following SummerSlam to have elbow surgery so they need to get the title off him.