According to The Wrestling Observer Newsletter Brock Lesnar has an option that would renew the deal and most expect that it will be renewed after it expires at WrestleMania 34.
The rumors of Lesnar possibly returning to UFC to fight Jon Jones. If Lesnar does decide to return to UFC for another fight, it likely would not happen until August since WWE would have no rights to him.
According to MMA Weakly White appeared on The Dan LeBatard Show this week and said he doesn’t believe WWE would allow Lesnar to fight again while he’s under contract. Vince allowed Lesnar to work the UFC 200 event in July 2016 but WWE ended up looking bad after Lesnar tested positive for a banned substance. White commented:
“They didn’t want to do that again. You saw what happened last time he was under contract and it doesn’t look good for anybody.”