That is simply not true. They have more than enough viable options, it's still 2 months until Mania after all. People are way too conditioned into thinking that the key Mania (Title-)Matches have to be set in stone and always be at least halfway done with the build already when the Rumble is over. ...especially with Elimination Chamber between it.
I mean heck... If Seth is too hurt to work Mania, then give Priest the title asap and have him defend it at Mania against Sami... or let Priest cash in the MITB beforehand to secure himself the Match at Mania because he's all tired and shit about all the missed opportunities. There is a shit ton you could do, it's not depending on one or two people alone.