#2 Retain titles - the Miz and John Morrison
The duo of The Miz and John Morrison just won the SmackDown Tag Team titles at Super Showdown. They were then forced to defend them in the Elimination Chamber after other matches were teased for the women (Lacey Evans in a promo) and by Sheamus via promo.
The SmackDown Tag division is mainly comprised of face teams (New Day, The Usos, Lucha House Party, Heavy Machinery), the Champs and the pairing of Dolph Ziggler and Robert Roode. There aren't a lot of other heel teams and we've seen plenty of runs atop the division by the New Day and The Usos. Regardless of their challengers, Miz and Morrison need to retain their titles if 'Mania goes down as planned.
They've displayed comedic charisma just like the New Day but also can back it up in the ring. With the potential of another face team joining the ranks in Daniel Bryan and Drew Gulak, it makes complete sense for the Champs to leave the Show of Shows with their belts. If a different team wins them then it would seem like
Creative didn't trust them atop the division. As The Miz has proven many times before, he can make feuds interesting when facing the right opponents. Morrison adds to The Miz's arrogance so well that it would almost be counterproductive to take the titles from them so soon.