Fun fact: The Rock has never (AND THE ROCK MEANS “NEVER!”) challenged The Undertaker at WrestleMania. If a showdown for the WWE Title is out of the cards for The Brahma Bull, there’s no reason he can’t throw the gauntlet down at the feet of The Deadman and attempt to surmount what has become the greatest challenge in WrestleMania history. The Rock and The Phenom have history together (they were even Tag Team Champions for a hot minute), but a collision on The Greatest Stage of Them All would — to use an old expression — certainly put a lot of butts in the seats. Besides, after interring Triple H inside Hell in a Cell at WrestleMania 28, The Demon of Death Valley will be looking for a top-caliber challenger (if he’s looking for a challenger at all), and a high-profile opponent like The People’s Champion certainly fits the mold.
Now this isn't confirmation or anything other than for us to simply speculate on, but the fact that they at least acknowledged the possibility of Taker/Rock shows that they are or have at some point thought about maybe Rock challenging Taker for the streak, and that it could happen. That being said I can't see it happening at WM29 regardless. If Rock wins the title from Punk at the RR, I can't see, nor do I want Taker and Rock fighting over the title as the match wouldn't need it. If Punk beats Rock, certainly it would have to be due to interference by Lesnar, or a Cena heel turn, and I can't see Taker turning heel to cost Rock the belt, nor just costing him the title for seemingly no reason.
The only way I could see Taker/Rock at WM29 is if Punk beats Rock by cheating on his own without anyone elses help, or the match ends with Punk getting himself DQ'd, which would be incredibly stupid. Taker/Rock at WM30 is a lot more likely, especially if Rock/Brock and Taker/Cena happen for WM29. If Taker/Cena doesn't happen at WM29 and instead it's Rock/Cena and Taker/Brock, then WM30 would have to be Taker/Cena and I can't see Taker continuing after that so a Taker/Rock match wouldn't happen unless Taker decided to keep going and fought Rock at WM31.