AJ Styles won the title shortly before Survivor Series last year. In 6 days, he will have officially held the title for one year.
On SmackDown, he tapped Bryan out cleanly and will face Joe at Crown Jewel in a match he's 99.9% guaranteed to win. There is nobody else on SmackDown that seems like they have even a slight chance of taking the title away from him other than MAYBE The Miz, but does the WWE feel they need to have the world title on Miz? I could very well see Styles holding the title until WrestleMania.
Also, with Reigns out, is Styles officially the #1 star in the company? He's always been treated like a God on the roster. He rarely loses. His matches usually go the longest on PPV by a wide margin. By all accounts he sells a ton of merch. I'd be shocked if he wasn't drafted to Raw next year.