7. Age
Let's say we do get The Undertaker VS Sting at WrestleMania 31. When the event rolls around, Taker will be 50 years old, and Sting will be 56 (their birthdays are a mere four days apart, with Taker being on March 20th and Sting being on the 24th). You don't need to be a math whiz to understand that combines to 106 years on this planet. Remember when everyone made "Age In The Cage" jokes about WCW having Hulk Hogan and Roddy Piper face each other in a Steel Cage at Halloween Havoc 1997? At the time of that match, Piper was 43 and Hogan was 44. That's 87 combined years, nearly
two decades less than what we'd see with Taker VS Sting. To further put that into perspective, in Mae Young's last singles match (October 11th, 1999, in a match with Ivory), she was 76 years old, and Ivory was 37. That's 113 combined years, folks. The big joke was that Mae Young was so very old when she was wrestling, and even then, her match barely beats out what Taker VS Sting would give us as far as combined ages is concerned. Obviously, Taker VS Sting at WrestleMania is a much bigger deal than Mae Young VS Ivory on a random episode of Raw, but the fact remains that WWE would be in some uncharted territory with having two people of such an advanced age headlining a pay-per-view for them.