Partial Source: Wrestling Observer Newsletter
The Undertaker vs. Brock Lesnar is now on the books for WrestleMania XXX, provided that Taker feels healthy enough to work that kind of match. Lesnar was always going to work with either The Undertaker or The Rock.
Both men (Undertaker & Lesnar) are not expected to appear on WWE TV until Wrestlemania season. Right after the Elimination Chamber PPV which is in February.