Del Rio is fully recovered from a groin injury, but is being given some extra time to recover to ensure he is fully fit for Wrestlemania 28. Del Rio returning now would also not fit in with current WWE storylines, as the majority of top names have a feud going into the Elimination Chamber PPV this Sunday.
Mysterio was also backstage at Raw in his hometown of San Diego. He has publicly stated that he wants to wrestle at Wrestlemania 28, but he still needs some more rehab after tearing his ACL last year. Mysterio was written from TV after Del Rio attacked him, so both of their returns will likely be tied in somehow.