Roman Reigns’ character change and becoming the top heel in WWE was one of the best acts brought by the company in recent memory. His transformation from a boring babyface to one of the most dominating heels in WWE had proved to be a good story-telling and, in turn, Smackdown received their undisputed top guy. He’s the reigning Universal Champion who looks forward to being clad with the gold for some more days.
Roman Reigns was rightfully chosen as the number-one draft pick in the 2021 WWE Draft as the Universal Champion for the Smackdown brand. He already has a title defense scheduled for Crown Jewel on October 21st against Brock Lesnar. But it appears that somehow the champion will manage to retain his championship as a reliable source is hinting at his next opponent.
Roman Reigns Completes 400 Days As WWE Universal Champion

During Wrestling Observer Radio, Dave Meltzer discussed the current depth charts on WWE’s main roster shows. He pointed out that SmackDown has a bit of an issue with the star power on the top of the card. Other than Drew McIntyre, no one can really challenge Roman Reigns for the title, instantly.
Drew McIntyre on Roman Reigns, “He’s The Final Boss In WWE”
https://www.youtube.com/watch?v=xN6opkvztoE
There’s a crisis in Smackdown main event scene
So, WWE might be having some trouble finding a main event name to wrestle him unless one of the names from mid-card status gets elevated. That being said, McIntyre should be the front-runner in facing the Tribal Chief, for now,
“The headliners side [on SmackDown] is exceedingly weak. If Roman Reigns gets through Drew McIntyre, your next level of guys is Sheamus and Happy Corbin as heels and Nakamura and Jeff Hardy [as babyfaces].” (transcription by Ringside News)

We will have to see the outcome of Roman Reigns vs. Brock Lesnar at WWE Crown Jewel on October 21st after which the landscape of the company will change, forever. Lesnar is a free agent, but in case, he leaves Saudi Arabia as WWE Universal Champion then the main event scene of Smackdown will be undergoing some major changes. In that case, the dynamic of the blue brand will be altered in a big way after the 2021 WWE Draft.
On a related note, Roman Reigns vs. Drew McIntyre in a rematch is heavily rumored since last year’s Survivor Series. Reigns cheated his way to victory and The Scottish Warrior can’t wait to get his hands on the champion and thereby take his title away from him.