#4. Jeff Hardy - AJ Styles' 2020 rival

Jeff Hardy defeated AJ Styles to win the Intercontinental Championship before SummerSlam 2020. However, his run on RAW has been a bit lackluster. Only feuding with Elias, Jeff Hardy seems to be low on WWE's priority list lately.
Even then, it only takes a few good matches for Hardy to regain his momentum. We've seen moments of magic, but WWE has to present that opportunity. AJ Styles and Jeff Hardy are both on RAW and don't have WrestleMania matches.
While this may not be the most enticing match for AJ Styles in 2021, an added stipulation could add heat to the match and make it exciting. If the two were to face off at WrestleMania, we would likely see their best bout to date.
There should also be high stakes on the line. If the two are to simply have a feud for the sake of it, the match at WrestleMania could be viewed as the "cool down" bout.
Since Jeff Hardy may not have many WrestleMania appearances left, a match against AJ Styles would be a good token of appreciation by WWE.