After last night's edition of WWE Monday Night Raw where Brock Lesnar assaulted WWE COO Triple H, Lesnar has been written out of WWE storylines for the time being and it's uncertain when exactly he'll be back. Ringside commentators Michael Cole and Jerry "The King" Lawler heavily suggested that Lesnar would/should be fired for his actions.
At this time, Brock Lesnar's future with WWE is very uncertain and has been described as being a "sticky situation." He didn't make any friends backstage at the Extreme Rules pay-per-view either, despite having a well-received match with John Cena.
Lesnar apparently went nuts backstage and threw a temper tantrum because he was upset about the whole match. Allegedly, the original plan was for Lesnar to physically destroy Cena and have Cena get carried out of the arena on a stretcher, making Lesnar look like a dominant force. But because Cena picked up the victory and was able to stand up and give a speech after the match, Lesnar feels that WWE made Lesnar look weak.
Lesnar also accused Cena of trying to blow out Lesnar's knee when Cena pulled down the top ring rope at some point during the match where both Cena and Lesnar fell outside to the floor.
There are some people backstage in WWE who suspected that Lesnar's temper tantrum backstage was all part of an act to make WWE officials bend over backwards for him and give him whatever he wants. He allegedly tore up the backstage area in a fit of rage that some people thought was all part of a performace to try to intimidate WWE officials into meeting his demands.
As of right now, a match between Brock Lesnar and Triple H is being planned for the 2012 SummerSlam pay-per-view, but it was also previously reported that Lesnar would be engaging in a feud against Randy Orton. These plans have seemingly been called off, at least for right now.
And as for Lesnar's longterm future with WWE, he might or might not participate at the 2013 Royal Rumble PPV, but he is definitely still expected to participate at WrestleMania 29 in 2013. After that though, there is a good chance that Lesnar will probably be finished with WWE.