Bray attacking Cena at the Rumble was just the early planting of the seeds for Cena/Wyatt at Mania. They're occupied with The Shield right now and Cena is focused on winning the title in the chamber, so the feud will pick back up and get off and running during the Wrestlemania build.
Expect the Wyatts to cost Cena the match for sure. I'd bet on them coming up through the ring like Michaels in 2010. And if Cena is the last guy eliminated, then the show could go off the air by having the entire family beat and pummel Cena all around the chamber (say after Orton picks up the pinfall victory, he hightails it out of there, obviously wanting no part of the Wyatts, and then they lock the chamber door behind them), similar to how Evolution beat the fuck out of Goldberg in the chamber (handcuffs and all) to end Summerslam '03.
That'd be a great night for the Wyatts - going over The Shield, and then presenting us with the final images of the last traditional PPV in WWE history, which is Cena being trapped in a chamber with all three of them and forced to feel their wrath. Picture Wyatt doing his pose in the middle of the ring with the chamber surrounding him while Cena lays unconscious and handcuffed and beaten to a pulp in the background.