As soon as it was revealed several weeks ago that WWE Champion CM Punk and Paul Heyman had forged a working relationship, speculation ran rampant with regards to Brock Lesnar's eventual involvement. There are plenty of possibilities, but I believe Lesnar and Punk will ultimately coexist peacefully.
Since Punk is all about himself as WWE Champion and Lesnar is a me-first guy as well, many believe that while Punk and Lesnar may start off as allies, one of them will eventually grow jealous of the other and start a feud heading into WrestleMania.
Although I won't say that there's no way something like that will happen, I'd rather it not and don't feel like it will. Punk vs. Lesnar may be able to sell to some degree, but if the goal is to elevate Punk to a different stratosphere, then he needs to face and defeat either The Rock, John Cena or both at WrestleMania.
Ideally, Lesnar will make his return at Hell in a Cell in order to help Punk defeat Cena. Lesnar isn't normally one to help out others, but he has always been obedient to Heyman, and he has a score to settle with Cena anyway, so it's almost as if Lesnar would be doing it for himself and Punk at the same time.
The biggest reason why I don't see a feud happening between Punk and Lesnar is the fact that both of them are much better as heels. Punk just turned a couple months ago, so I would be shocked if he turned back prior to WrestleMania. Also, while Lesnar does have a sizable fan following, everything about him screams heel, so a face turn would be ill-advised.
Lesnar's mic work is terrible at best, so he needs the likes of Heyman and Punk to do his talking for him. He was given one opportunity to cut a promo during the contract signing for his Cena match and it was absolutely awful, so I doubt that the WWE is willing to subject its fans to another rambling, senseless Lesnar rant.
Turning Heyman face along with him is an option, but Heyman is a natural heel and wouldn't be nearly as entertaining in a different role. I realize that Lesnar may not want to play second fiddle behind Punk, but based on the fact that the WWE is paying him millions of dollars to make periodic appearances and wrestle a few matches, I'm guessing he'll be a good solider regardless.
There are plenty of good things that Lesnar can do aside from going after Punk and his WWE Championship. The most obvious one is a match with The Undertaker at WrestleMania, which is something that many fans have been waiting a very long time for.
If the goal is to put over a younger guy on the full-time roster, though, Sheamus and Ryback are good possibilities in terms of WrestleMania opponents. I'm not a huge Ryback fan personally, but based on the fact that Ryback and Punk seem poised to engage in a mini-feud, I could most definitely see Lesnar and Ryback mixing it up.
At Survivor Series, there could be a tag match either pitting Punk and Lesnar against Cena and Ryback or an expanded eight-man match involving those four guys. From that point forward, Punk and Lesnar would technically still be part of the same stable, but they would be focusing on their own affairs with Punk against Cena and Lesnar against Ryback.
In other words, Punk and Lesnar will be allies to some degree, but they'll both be looking out for their own interests as they often do anyway. I initially thought that we might see a big Heyman-led stable, but the more I think about it, the more it seems like we'll just see a loose partnership between Punk and Lesnar formed on the basis of Heyman's presence and a hatred of Cena.
The WWE has an opportunity to do something special with both Punk and Lesnar moving forward as long as they are put in the right situations. A Punk vs. Lesnar feud would be decent, but I fear that Lesnar's deficiencies would be exposed, so I do believe that Punk and Lesnar will find a way to work together whenever Lesnar returns.