Cody definitely seems a safer bet than Christian. If there's one recurring theme it's that briefcases are tailor-made for heels to win and cash in on vulnerable, otherwise-nigh-undefeatable faces. Heck, even when Daniel Bryan won and cashed in he started heeling it up afterwards... so, Cody or Wade for sure.
I guess Cena is still the pick to win the other one but he'd be all noble and declare that he's cashing it in for the Summerslam main event.
EDIT: forgot about Ziggler, he could still qualify and win it.