Nah, not feeling the logic. Rock doesn't need a WWE return. In his last match with Cena, he tore his abdomen and supposedly cost lots of movie employees their jobs because he couldn't film for ages. He didn't make Mania last year from Hollywood when it would've been perfect.
This is his last match IMHO and it's the perfect way for him to go out. A Rock/Roman match wouldn't incur much good will in this day and age, especially if it sucks bell to bell. The casuals will lap it up but the live fans will poop all over it.
This also makes Cody huge. Rock's known him since he was a child and they're family friends. Rock doesn't need or want to make Reigns as, let's be honest, Roman is probably going to parlay away from wrestling or go even more part time soon. He'll either go into Hollywood too or look after his family and health. Roman doesn't need to be made. Cody arguably does. This also crushes any 'Cody's been over-pushed, he's a manufactured white meat baby face' blow back that many suspected would soon happen and did happen in AEW.
It will make the WWE lots of money and is much more compelling than Roman/Rhodes 2 or Rock/Roman. Putting Cody in to make it a triple threat makes all the sense in the world to protect Rock from an in ring point of view. It's actually perfect.
For me, this has Paul Heyman's fingerprints all over it. He's apparently been all over the creative concerning the Bloodline. He likes blurring the work/shoot lines and getting people talking.
The only unknown is Seth's role. I assume they had him back up Cody because 1) they might have a four way, 2) due to Seth's injury, they're hedging their bets because a one on one match puts him at more risk and 3) it makes so much sense given his history with Reigns and Cody.
I suspect they'll somehow have McIntyre or Gunther take the belt off Seth before Mania. Maybe even thanks to Rock or Roman in a really quick match, protecting Seth's knee. Then Sami Zayn will face the new champ at Mania with Damian Priest hovering.
In the Reigns/Cody/Rock(/Seth) main event, Solo and Jimmy will likely get involved but Rock will stop them and Cody will win. Mania will end with Rock lifting the new champ Cody's arm.
From there, I guess they might do a Rock/Roman singles match in Saudi (depending on how Rock feels), turn Knight or Orton heel again to feud with Cody, have Seth go for whoever he lost the World Heavyweight belt to and eventually have McIntyre/Punk and later Punk/Reigns (probably at Mania 41 after Reigns has barely been around). They'll super push one of Bron Breakker, Carmelo Hayes or Trick Williams with a view to one of them maybe facing Cody at Mania 41 for the Universal Title. Just my guess.