What Morrison needs is a dominant, already established, heel champion to go after with a Rumble win. And right now, there isn't one. That is the only way his push to the main event of Wrestlemania would work. The Miz, is not the answer to that for Morrison right now. As it is, Miz himself needs an already established star to face at Wrestlemania to solidify his spot..so it just wouldn't work. While there is a decent amount of history between Miz and Morrison, Miz doesn't hold the main event name value of one of the veterans. Furthermore, the "history" between Morrison and Miz is not the makings of a Wrestlemania caliber feud - maybe any other PPV, but not Wrestlemania. They use to be tag champs and have faced each other here and there in mid card grudge matches...OK who cares? Yeah, there has always been some bad blood between the two, but let's not forget that the first Raw of 2011 was when Morrison got his first WWE Title shot and Miz had his first real title defense (not counting the tables match with Orton). The story isn't there yet for the two to face for the WWE Title at Wrestlemania.
Putting these two superstars in a match against eachother for the WWE Title, on the grandest stage of them all, while both are in the midst of huge pushes, would be stupid and ulimately hurt one of them in the end. While Miz is the current WWE Champ, he still has not been completely accepted by most fans as a credible main eventer and he needs to continue to be pushed in feuds with already established main event talent moving into Wrestlemania. Morrison on the other hand, has been on a hot streak, looking to break into the main event scene as a big baby face, but still isn't quite there yet. The pushes are at the same place in my eyes because as a heel, a superstar needs to get over as Champ, where as a baby face needs to get over before he becomes Champ. Neither Miz or Morrison could afford a loss to the other right now, especially not at Wrestlemania. Either outcome of a Miz/Morrison WWE Title match at Wrestlemania would be a lose/lose situation.
Let's look at the two scenerios: If The Miz were to lose the WWE Title to Morrison at Wrestlemania, his credibility as a main event star would be completely shot down to a point where he may never recover. And the bigger question becomes, would people care to the level that they should regarding the WWE Title at Wrestlemania? Let's not forget to mention that Morrison winning the belt off The Miz would hardly prove that Morrison can hang in the main event (at Wrestlemania no less) because the person he would be beating hardly has main event cred to his name at this point. On the flip side, Morrison winning the Rumble, then to go on but ultimately fail in capturing the WWE Title at Wrestlemania, would destroy Morrison and be an absolute waste of a Rumble win.