#5 Batista
Batista has always said that he wants his last match in WWE to be with Triple H, however, that may have changed after his terrible run in 2014. Batista was booked poorly throughout, through no fault of his own (apart from his dress sense), and a return to WWE looks highly unlikely.
However, money talks in wrestling and the timing is pretty good for both parties. Batista would probably like to promote Guardians of the Galaxy 2 to a massive audience, prior to its release, shortly after WrestleMania.
From the WWE’s stand point, they simply need a credible opponent who is equal to or bigger than Seth Rollins. The last time we saw Batista, he was quitting Evolution, which is a perfect place to pick up, if he were to return to the WWE.