The Undertaker is expected back on WWE TV this week and will “likely” be on Raw, according to PWInsider.
Whatever he does will be setting up his match at WrestleMania, which as of now is rumored to be against Roman Reigns. There was some tension teased between the two at the Royal Rumble.
Undertaker could also possibly get involved somehow in the Roman Reigns vs. Braun Strowman match at Fastlane. Seems unlikely that that match will have a clean finish, since WWE doesn’t want either Reigns or Strowman looking “weak.”