Taker/Punk, Taker/Jericho, Taker/Ziggler, Taker/Knox, Taker/Matt.
They're our options for Taker on Smackdown assuming nobody switches from heel/face, face/heel.
Obviously the way WrestleMania is, it seems like the heel champion for Smackdown will be either Jericho or Punk, and Taker will most likely feud with the other one. Taker/Jericho is a much bigger match for Mania, but Edge/Jericho is a much bigger main event than Edge/Punk or Morrison/Punk. Personally, when it comes to WrestleMania, I think it would be better to have Edge/Jericho if they can, and if not, Morrison/Jericho, and put Punk/Taker down. Jericho and Undertaker is a huge match, but I think it might be better served for Survivor Series, seeing as how Undertaker doesn't fair too well being a part of a team, and they've already got more than enough other people to fill in those roles (Mysterio, Finlay, Morrison, R-Truth, MVP, HBK, Kofi, Bourne, Christian).
Taker/Ziggler over the Intercontinental title would elevate the championship a HELL of a lot. When's the last time you saw the Undertaker feuding over the INTERCONTINENTAL title? I'd love to see it.
Taker/Knox is a throwaway feud. The standard "two big men; Knox gets his ass kicked" situation.
Taker/Kane...I think they should stay away from that, seeing as it most likely will be Undertaker's retirement match. Don't do it until that happens.
Taker/Matt could work as an upper midcard type of feud. Naturally, it depends on when the two of them return. This would be the better match to start off with, I think, as Ziggler can beat the crap out of Finlay and get a much needed boost in the meantime, which would allow us to believe that he could have a legitimate feud with the Undertaker, instead of going directly from the smallest guy (Mysterio) to one of the biggest guys (Taker).
So yeah, I say, when Taker returns, if Matt's healthy enough, start off with those two. If not, feed Mike Knox to the Undertaker until Matt's healthy. Then you go to Ziggler. Then around Survivor Series, Taker/Jericho for the title. Around the Royal Rumble, you have Taker/Knox if you haven't done that already. Then you start Taker/Punk for WrestleMania. After that, its draft time.