According to The Wrestling Observer, the new idea for the WrestleMania 31 main event is Bryan vs. Reigns vs. Lesnar for the title.
Plans could always change between now and the Fastlane pay-per-view on February 22nd but the current idea is to do a Triple Threat at WrestleMania 31 after Vince made the decision, apparently due to the crowd reactions.
CREDIT / SOURCE - The Wrestling Observer