While it is unlikely the midcard titles get defended on the main show, I'll bite and include them. So here we go.
Divas Championship-Beth Phoenix (c) vs. Natalya
-Beth is tired of Nattie's constant losing and turns on her Divas of Doom partner. After avoiding Nattie for much of 2012 she finally gets her shot at the title. Beth wins in sneaky fashion, but expect Nattie to get that butterfly title within a month or two after Mania.
United States Championship-Zack Ryder (c) vs. John Morrison (or Kofi Kingston)
-Ryder finally gets his moment and becomes a singles champion. Morrison in a losing slump finally loses it and takes out his aggression on Zack Ryder. If not Morrison, Kingston loses it and takes it out on Ryder (who substitutes for Bourne in a title defense). Either way Ryder wins and furthers his rise in the ranks.
Intercontinental Championship-Cody Rhodes (c) vs. Justin Gabriel
-I wasn't sure of an opponent for Rhodes, so I went with Gabriel. I went with Gabriel pretty much the same reason as I picked the Usos in the next match. Gabriel certainly has potential and Rhodes can do wonders by getting him some mid card exposure. Rhodes retains, but it sets up an inevitable win for Gabriel.
WWE Tag Team Championship-Ziggler and Swagger (c) vs. The Usos
-If not the Usos substitute a new upstart team. This is the chance for said team to shine on the biggest stage and win the tag team gold. With Air Boom in jeopardy due to Bourne's suspension I expect a ZigSwag to finally get the titles. If they want to make the tag titles something, what better way to elevate a team than giving them a WM win.
World Heavyweight Championship-Sheamus (c) vs. Wade Barrett
-Sheamus dethrones Mark Henry as champion and Wade Barrett is hot entering 2012 and looking for the title. He finally accomplishes that goal, but it don't last long as Daniel Bryan cashes in and lives up to his word. He defeats Barrett and wins the title and sets up an instant feud.
WWE Championship-The Miz (c) vs. CM Punk
-CM Punk is coming off an amazing Rumble win after chasing after the championship for the end of the 2011 and starts off 2012 with a boom. Miz gets the title either at the Rumble or in the Elimination Chamber. CM Punk takes the championship here in the Wrestlemania moment that is needed.