I a going to go out on a limb here and say that he will wrestle in the main event of WrestleMania. Personally, I think that depending on what the WWE do with him over the next couple of months, he could be the ideal foil for a great feud against one of the top faces. The Miz has a lot of talent and even more potential. He has turned haters into believers and he could easily become one of the most over heels in the company. They still have 4 months to get The Miz into a position where he could be called a legitimate dominant champion, through hook or by crook. Sure, right now The Miz seems to be hanging by the skin of his teeth but who knows what the future could hold for him.
So let us have a look at what probably lies down the road for The Miz. He will likely face John Morrison at the Royal Rumble and I would assume that he will be the one who comes out on top of that affair. I just don't think that the WWE have enough faith in Morrison to have him carry the belt for any amount of time at the moment. The reports that Vince is high on The Miz have been a permanent fixture over the last couple of months and the same reports have not come out about Morrison. Sure, he is on a mega-push right now but they wont put him over The Miz this soon, especially when this year has basically been about pushing him to be the WWE Champion. At Royal Rumble, The Miz will likely go over John Morrison and will head into Elimination Chamber as Champion.
Who knows who will win the Rumble but I personally believe that it will be a face, at this point. Whether it will be someone like Triple H, John Cena or someone a little lower on the card, I think that a face winning the rumble is a lock this year. Perhaps the safest bet would be a Triple H win to accompany his return but who knows. For me though, a big face has to win the Rumble to allow The Miz to main event Mania. The Miz, on his own probably wouldn't pull in the buys for the WWE right now. They would need to put him in the ring against someone who would and the only people I can think that would do that is Triple H and John Cena.
Anyway, when you move onto Elimination Chamber, things become a bit more crazy for The Miz. If Triple H wins the Rumble, which I think he likely will, it would leave him free to face whoever he wants at Elimination Chamber, knowing that his place at Mania is secure. That would give him time to end his beef with Sheamus and go onto WrestleMania. Maybe have that match be for Triple H's shot at the title at Mania. Either way, Elimination Chamber will be the biggest test of The Miz's fortitude and if he can come out of that one with the title, then I will be very surprised. However, at the same time, it would be the best idea for the WWE if they are trying to build The Miz into a huge star.
For me, I think The Miz will be in the main event of Mania. Probably against someone like Triple H or John Cena. However, I do think that John Cena and Randy Orton will be the biggest match on the card. Keeping Cena out of the title match would probably make some sense if they want to pull that off.
And then, of course, you have to consider the unification of the belts. If they are to be unified, the only person I could see The Miz going up against is Edge. That would be pretty fresh and interesting, I think. I do think he will make it to Mania but I doubt he will be coming out with the belt if he meets Triple H in the main event.
We shall see.