Taker.
He's never won it.
Batista sucks as champion.
Taker's due one more title run.
Smackdown is in desperate need of something fresh, and a Deadman title run would probably do that.
Smackdown has had SO many new guys that they need to spend some time on an actual established name, character, and wrestler people remember who can still go despite his age.
Batista/Taker has possiblity of being somewhat decent, and probably Batista's best match yet (which isn't saying much.)
When Taker loses the title, he can put someone over big.
Can lead to a feud with Edge when he takes a break after he loses the title and returns before Wrestlemania 24 in an Undefeated vs. Undefeated match.
With that said, Randy Orton will win it.