As much as I like Ziggler, he's not ready to face Edge for the world title at WrestleMania. I wasn't even expecting him to be the one facing Edge at the Royal Rumble. Now, I'm thinking if they have MITB at Mania, Ziggler is within top contention to win it.
So if Edge goes into it the champ, who faces him? Well, I'm not a huge fan of pushing people too far, too fast, but I can really see Del Rio facing Edge. I don't think it is the smart decision, though. I like Del Rio, but I don't think they should have him peak so early. Instead, I'd rather it be a returning Christian. I like Ziggler but if he's having a title match at Royal Rumble, then there's no reason to repeat it at Mania. We've already seen it.
Now, I'm not saying Christian for the whole "I want to see those two together so badly" reason that a lot of people do. I'm saying Christian because it would be a big enough match to warrant being the 3rd to last match on the card. We know Smackdown won't have the main event, and it'll be pushed down further, so that's the best they could do. Christian turns heel and faces Edge. His injury is a problem, yes, but with these two, you don't need that much of a build, so if he's good enough by Elimination Chamber, then you're fine. Really, all Christian needs to do is attack Edge once to turn heel and then the two cut some promos and you've got your match. And Christian winning wouldn't make sense as they clearly don't trust him to be their champ, so Edge retains at WrestleMania - then, hopefully, starts a program with Wade Barrett and drops it to him after he's done with Taker.
But really, I think the story here is the WWE championship match. Currently, I'm working under the assumption that it'll actually be a four-way for the title between Orton, Cena, Miz, and CM Punk. I can't see Miz retaining to face Cena, cutting short the Cena/Punk feud, and I can't see Miz continuing to feud solely with Orton, and I can't see Orton winning the title from Miz and then suddenly rushing a feud with Punk, so that's the only way to incorporate these guys, I think....unless Miz drops the title in the Elimination Chamber to CM Punk because of something Orton does and then the two have some sort of grudge match at WrestleMania...but I think that would be better served as a spot for HHH vs Sheamus in some kind of no-dq match instead.
So yeah...my vote right now is that I expect it to be Del Rio, but I'd rather it be Christian.