Reigns returned at the end of SummerSlam last night to take out Braun Strowman and new WWE Universal Champion "The Fiend" Bray Wyatt. Bryan Alvarez noted on Wrestling Observer Live that he was under the impression at one point that Reigns may be appearing on RAW tonight.
It's not confirmed that Reigns will be appearing on RAW, but last night's return indicates that he will remain on the SmackDown brand.
On a related note, the friendly Instagram back & forth between Reigns and Randy Orton continued this afternoon after Orton compared The Big Dog to the donkey character from Shrek. For those who missed it, Orton first made a friendly jab at Reigns over the recent dental work he had done while away from WWE.
You can see the full Instagram exchange between Orton and Reigns below: