The current plan for WWE Universal Champion Brock Lesnar is for his next title defense to be on August 19th at the SummerSlam pay-per-view in Brooklyn, according to the Wrestling Observer Newsletter. Lesnar is set to headline that show, although that could always change. No word yet on who his opponent will be.
Regarding a potential UFC return by Lesnar, he will almost certainly be staying with WWE unless he applies to be put back into the USADA testing pool for UFC by June 30th. If he is headed back to the Octagon, a fight at the UFC New Year's weekend event is likely.
With Lesnar not working the July 15th WWE Extreme Rules pay-per-view in Pittsburgh, it looks like the top RAW match will be a six-man match as the PPG Paints Arena has Roman Reigns, Braun Strowman and Bobby Lashley vs. Sami Zayn, Kevin Owens and Jinder Mahal advertised. With that bout, it would appear that a WWE Championship match will headline the show.
Other matches advertised for Extreme Rules are Daniel Bryan vs. Samoa Joe plus appearances by Styles, Shinsuke Nakamura, WWE Intercontinental Champion Seth Rollins, WWE United States Champion Jeff Hardy, Finn Balor, The New Day, SmackDown Women's Champion Carmella, RAW Women's Champion Nia Jax, Charlotte Flair, Alexa Bliss, Sasha Banks and Asuka. In addition to Lesnar, John Cena and Ronda Rousey are not advertised for Extreme Rules.