The biggest news coming out of WrestleMania is the breakthrough Vince McMahon and Brock Lesnar had in negotiations on Thursday, leading to Lesnar signing a new deal that will allow him to fight in UFC as often as he wishes. The new deal is a 1 year deal with many options on both sides for extensions. While Lesnar isn't technically taking a pay cut, WWE will be paid a flat fee, believed to be in the $250,000 range, whenever Lesnar has a UFC fight.
The confrontation backstage after WrestleMania was 100% a work intended to further a storyline that Lesnar would be attempting to leave the company with the belt. When WWE got word that it was going to leak that Lesnar had resigned, WWE went ahead and made the announcement themselves, and reversing course on the plan to act like Lesnar was champion without a contract.
UFC has no problem with Lesnar staying with WWE as it's Lesnar paying WWE the $250,000 fee when he fights, not UFC, and UFC believes the WWE television exposure simply enhances Lesnar's drawing power on pay-per-view for UFC.
Brock is currently (As of Saturday) not back in the UFC testing pool, however I was told it would be in the next month. Brock has to be back in the testing pool for 6 months before he can fight in UFC. The current plan is for the winner of the July 7th UFC 226 Miocic vs. Cormier fight to face Brock at the end of the year.