Prior to being seen at UFC 184 with Dana White, it was reported that Brock Lesnar walked out of WWE Raw likely due to issues with his contract with the pro-wrestling organization. As Dave Melzer reports, apparently there was also a heated argument between him and WWE head Vince McMahon. From f4wonline.com (via CageSideSeats):
"There was a heated, loud discussion where Vince and Brock were yelling and screaming at each other, loud enough where other people were concerned, especially for Vince because it really sounded bad."
Also according to the Observer, apparently the WWE writing team asked Vince McMahon if they needed to write an alternate story for WrestleMania after the Lesnar situation, and Vince emphatically said "no."
WWE of late has been trying to insert unusual stipulations into their talent contracts like extended non-compete clauses, and has also gotten the reputation for verbally agreeing to terms with wrestlers only for the written contract to come back different. Those tricks might work with the average WWE wrestler, but clearly Brock wouldn't put up with such crap.
... Unsurprisingly, according to Meltzer, UFC management are more confident than ever thatwill return to the Octagon later this year.
A couple of days after the heated argument, Lesnar made an appearance at UFC 184 in California. White of course had been asked about this, and stated that he simply isn't allowed to negotiate with Brock just yet.
"Apparently Brock Lesnar is a UFC fan, and he was in town and wanted to come see the fight tonight," White said during the UFC 184 post-fight press conference. "He’s under contract with the WWE, and when his contract is up, I’m sure he’ll call me."
While many people assume that showing at an event means Brock is making a return to MMA, it's actually more of a power move as he moves closer to the end of his WWE deal.
White isn't going to tamper and interfere with someone under contract, and Lesnar knows this, but even a simple appearance at an MMA event instantly sends a message to the WWE. There are other suitors, and the best bidder among the three -- including Bellator -- will be the only one to get his services.