According to an April 21 post from Bleacher Report, Sting is being looked at for a double-retirement match against The Undertaker at Wrestlemania 31. Sting, who spent most of his pro wrestling career under the TNA banner, is perhaps the most popular wrestler to have never competed under the WWE banner.
Sting, 55, is in the twilight of his career, but most wrestling fans are still interested in seeing him fight in the WWE at least once. The WWE is fully aware that Sting has value as a wrestler, so they intent to use him for one single bout before the legend hangs up the gloves for good. Sting's WWE debut will likely happen at Wrestlemania 31, and he's expected to ride off into the sunset following the event.
The WWE hasn't made any official announcement on who Sting will take on at Wrestlemania 31, or if he's even actually going to be on the card. However, it would make sense for him to take on The Undertaker. WWE Universe has been interested in a Sting vs Undertaker bout for many years, so Wrestlemania 31 could provide the perfect event for a send-off of two legends.
The WWE has also been giving young bucks such as Roman Reigns and Daniel Bryan spots in the limelight this year, so setting up either one of them against Sting would be huge resume-boosters for them. So far, Sting hasn't officially signed his name on the dotted line to compete for the WWE. However, he recently made an appearance on the WWE Network, during an Ultimate Warrior tribute show.
Sting's appearance on the WWE Network would seem to indicate that he at least has a working relationship with the WWE. Since Sting's WWE debut is so anticipated, chances are the WWE will wait until a massive event goes down before revealing him to the crowd. That event will most likely be Wrestlemania 31.
Other dark horse candidates for Sting's WWE debut include Bray Wyatt, or even The Rock. Time will tell how the situation plays out, but it seems clear Sting is inching closer to his WWE debut. The WWE still has several months to figure out how to handle the situation.