Firstly I have not included Chris jerhico or Cm punk because I don't think jerhico Is the right person to face undertaker at Wrestlemania and punk had a lengthy feud with him a few years back (I also think they will both be feuding over the wwe title).

Secondly, I think whoever faces Undertaker at Wrestlemania should lose to *keep his legacy so he can retire 20-0.

The Miz
He's great on the Mic and decent enough in the ring. He could state that like undertaker he is also unbeaten at Wrestlemania. Although I don't think this will happen because taker's recent Wrestlemania feuds have revolved more around acting rather than talking and the miz doesn't have enough in ring experience yet.

Triple H
They had a great match this Wrestlemania and he's a veteran*who can carry the match but I'd prefer taker to face someone new this year rather than having him face taker at 2 consecutive wrestlemanias like with HBK.

Mick Foley
If this was the case then this would probably also be foleys last match which would take away from undertakers retirement match (if he was to retire) a little. He's a veteran though and could carry the match but I don't think they'd be able to replicate the quality of the matches they had previously so it could leave fans disappointed .

Wade Barrett
This feud would revolve around the nexus attacking him during his buried alive match with Kane but he lacks some of the experience the others have and I think he'll be involved with the world heavyweight title at that time. He might even win the royal rumble.

Kane
This match is a high possibility as undertaker and kane have unfinished business after their previous fued. They could do something similar to with triple h where Undertakers return is interrupted by a returning Kane wearing his mask with his old theme music. Or Kane could win the rumble and rather than choosing to have a title shot he chooses to have ago at ending Undertakers streak.
Kane is experienced and has worked with the Undertaker a lot previously.

Christian
I'd like to see this match, they could have undertakers return I interrupted by Christian who says he's never had the chance to end takers streak and he knows he can do it. Christian's an experienced veteran who's never had the chance to end the streak and can carry a match. His mic skills and in ring work are top notch.

I'd like to see undertaker/kane or undertaker/Christian most.*I think taker might have 2 matches left in him and I'd hate to see his retirement match overshadowed by rock/cena.
They could have Wrestlemania 28-cena/rock, Wrestlemania 29-undertaker/Kane or Christian and then Wrestlemania 30-punk/Austin.
*
When undertaker retires it'll be the focal point of that Wrestlemania and I'd like it if at the end everyone who he's defeated at Wrestlemania came down to the ring and shook his hand (or something to that effect).

Thanks for reading and i look forward to reading the comments.