Update on WWE Changing Extreme Rules Main Event & Lesnar’s Status

According to Dave Meltzer in a recent edition of The Wrestling Observer Newsletter, the change from the Multi-Person Main Event Matchup that was originally scheduled for WWE Extreme Rules was said to be a “panic move”, though it is unclear why. The original participants were supposed to be Roman Reigns, Bobby Lashley, Finn Balor, Baron Corbin with the remaining two wrestlers unknown.
WWE explained the change by blaming it on difficulties with Brock Lesnar and his refusal to agree to wrestle the winner of the match, but that is all storyline and Lesnar is tentatively scheduled for SummerSlam as having to face the winner of a potential Roman Reigns vs Bobby Lashley Match. The overall plan is still for Reigns to be that guy and get his rematch from the Greatest Royal Rumble fluke finish.
Source: Wrestling Observer Newsletter