Per WWE.com's synopsis:
"On a special Memorial Day edition of Monday Night Raw, “Mr. Money in the Bank” Brock Lesnar is expected to announce which World Champion he will cash in his contract on. Will The Beast Incarnate target Universal Champion Seth Rollins or WWE Champion Kofi Kingston?"
The most likely target for Lesnar seems to be Rollins, based not only on his losing of the Universal title to Rollins at WrestleMania 35, but Rollins' current lack of opponent for Super ShowDown on June 7. Kingston is already tabbed to defend the WWE Championship against Dolph Ziggler at the event.
This would mark the second straight year that the men's briefcase had the cash-in called in advance. In 2018, Braun Strowman challenged Universal champion Roman Reigns in advance of their match at Hell in a Cell.