I'm told Vince McMahon hoped all weekend that Brock Lesnar would be able to appear at Wrestlemania but there were a few things standing in the way. More than anything, the issue was making sure the deal was signed before he was allowed to appear in front of the crowd. Even though Brock and WWE had been in talks for some time, it was only within the last week that Vince wanted him to return at Wrestlemania as opposed to on Raw Supershow sometime in April, so that really put a squeeze on how much time there was to get everything done.
Another issue though is that Vince hadn't made up his mind 100% on who Brock would wrestle at Wrestlemania XXIX next year, and Brock's side didn't see the point in rushing to get a deal signed in time for him to be a surprise at Wrestlemania when Vince was still going back and forth on who the opponent would be. The three opponents being considered are The Undertaker, The Rock and John Cena
Complicating things further is the fact that Steve Austin vs. CM Punk is on the company's wish list for next year, but Austin hasn't fully committed to a return.
There are some in WWE who are against doing Brock vs. Undertaker or Brock vs. The Rock, feeling the big match for next year shouldn't be between two guys who aren't full time members of the roster. That is why Brock vs. Cena has some supporters. However, the counter to that is, if Austin is returning as well, Austin facing a regular roster member calms some of the concerns of having Brock face a guy like Undertaker or Rock, who don't appear often.
So, without knowing if Austin is really going to end up agreeing to return to face Punk at Wrestlemania XXIX, it's hard to factor that into the decision making process in regards to Brock's opponent.
I was told that while Vince was disappointed they couldn't get Lesnar to sign yesterday, he didn't want to push so hard that he risked Brock walking out on the deal, so Brock was never given an ultimatum or anything of the sort in regards to signing in time to appear later in the day on the pay-per-view.
Once WWE sorts out who Brock will be facing at Wrestlemania next year, some of the plans for other big shows will fall into place.