As seen on the 900th episode of WWE Smackdown, The Undertaker made his return to WWE programming and announced that he was not going to let WrestleMania define his career.
He basically announced that he would be working events outside of WrestleMania moving forward, however we have not heard or seen from Taker since.
The belief is that with so much time in between pay-per-view events from December to January, WWE could be prolonging his return to television until the year end nears or have him return the first couple weeks of January. Once he returns, he is expected to challenge AJ Styles for the WWE World Title, presumably at the Royal Rumble.