I'm pretty certain the idea right now is to probably have Sheamus fail his cash-in at Wrestlemania. Whether Reigns wins the championship at Survivor Series or Wrestlemania (I imagine they probably want it to be the latter, since winning the gold for the first time on the grand stage feels much more special and monumental, especially of a guy they want as the next face of the company), Sheamus will probably try to recreate history by cashing in afterwards but then end up eating a spear out of nowhere and losing. It'd be a ideal way of Reigns' getting redemption for getting cashed in on this year.