-- As noted before, WWE has refrained from booking Braun Strowman into a match at WrestleMania 34 because he's been pegged as the "backup" if the Roman Reigns/steroid situation becomes a mess. The feeling was that it was better to leave him out of a match in case something changes rather than scheduling him in something else and then being forced to reshape the card if something bad happens with Reigns.
-- At this time, if Lesnar vs. Reigns goes on as expected, the plan is for Strowman to not even wrestle at the PPV but instead be involved in a "non-wrestling gimmick thing."
Source: Wrestling Observer Newsletter. Subscription information & prices available at f4wonline.com