Mark Henry and Ryback have recently had a lot of awkward, unexplained stare downs backstage. I can only assume Mark Henry is jealous and trying to prove himself to be the vicious, unmerciful monster he used to be. Recently, Ryback has taken that role from him while he was out with an injury. Because of this, Mark Henry stepped into the ring and distracted Ryback, allowing The Shield to beat him down further, and then performed his own finisher, the World's Strongest Slam on him.
The most likely situation is that Ryback will turn down Sheamus and Orton in favor of taking on Mark Henry at WrestleMania. This is the most predictable and most boring outcome and would have the most negatives. Mark Henry, for several months, was an important player on SmackDown but lost all of that momentum when he was out with his injury. He has made such a big step in being able to return, that it would seem detrimental to the WWE to have him lose at WrestleMania. However, Ryback is the new muscle monster on RAW, and stepping away from The Shield match to face Mark Henry would cause Ryback to take a step down from a more interesting and important match. Ryback has already been losing momentum and interest from viewers, and losing to Mark Henry might kill off everything he has built in the last year.
While WWE has always enjoyed lining up big men to face off against each other, Mark Henry and Ryback is a career killer. One of these hardworking superstars is going to fade into obscurity because of this loss, the WWE just needs to decide whether it will be the SmackDown's older World's Strongest Man, or RAW's ever hungry Ryback.