As noted before, The Undertaker vs. Triple H is indeed one of the matches on the books for WrestleMania 28. The talk is that Taker will return in early 2012 to pick back up on the feud with Triple H.
The pre-sale password for the Elimination Chamber pay-per-view in Milwaukee, Wisconsin is CAGE. Tickets go on sale via Ticketmaster this Friday, December 16 at 10AM local time.