John Cena and Sheamus are expected to make returns at the WWERoyal Rumble in January, as surprise entrants in the Rumble match itself. Of course, this all depends on their injuries and how fast they are able to rehab.
This would likely mean that other current or former stars will be making surprise returns at the event this year. Jake "The Snake" Roberts had been talking for months about being a part of the 2014 Rumble, but may not do it this time with both Cena and Sheamus likely returning.
Plans could always change between now and January, but this is currently what is being planned. John Cena previously made a surprise return at the 2008 Royal Rumble.