At WrestleMania XL this past weekend, WWE had planned to use The Undertaker, Steve Austin, and John Cena; however, they were only able to secure the services of two legendary figures.
Austin has not appeared at a WrestleMania since WrestleMania 38, when he returned from retirement for his first match since 2003, defeating Kevin Owens in the night one main event. WWE attempted to book him for another match at WrestleMania 39, but he was unable to do so because he was filming his reality series for A&E at the time.
WWE did have Cena and Taker appear in the main event of night two, Cody Rhodes vs. Roman Reigns for the Undisputed WWE Universal Championship. This was when The Bloodline, Seth Rollins, Cena, and Taker got involved, with Cena laying out Solo Sikoa and Taker choke slamming The Rock.
According to Dave Meltzer of the Wrestling Observer Newsletter, Austin was originally scheduled to appear at the end of the match where Taker laid out the Rock.
However, Austin was not present because they were unable to reach a financial agreement, and Undertaker took his place.