Plus, the "streak" is over. From a story line perspective, that was always the selling point. Anything with Taker now is just another match. Even if someone beats him at Mania, so what? It's been done.
That is why it was the most BONEHEADED move McMahon had to end the streak, especially with the Undertaker in his Deadman gimmick. I could somewhat stomach it happening with the Biker gimmick. But, given how many times Lesnar beat 'Taker then, a loss at WrestleMania might not have had as much shock value.
WrestleMania was about three big bouts: The two world title matches and "The Streak Match" vs. Taker (unless 'Taker was involved in a title match, i.e. WM23 and WM24).
The match at WM29 was the biggest match Punk ever had. Many thought he would end the streak. I even thought it was possible until Paul Bearer died (you may recall my thread about that from two years ago).
Taker vs. Sting would have been GIGANTIC, just on hype alone. If the Deadman were able to whip himself into shape, ala 2007, LOOK OUT!!! 22-0 vs. the last WCW mohican, the vigilante.
Now, we get bupkus, unless they go Sting vs. Lesnar. And THAT only happens if they let Rollins cash MITB on the Beast.