I remember reports coming out from 1999-2000 that Undertaker was "thinking of packing it in". Whatever, don't believe anything you read but what I'm saying is that rumors of his leaving have been going on for years.
I agree that if the streak ends it should be Kane. The problem though is that Kane probably doesn't have too many years left either so it really wouldn't be beneficial to him. So really the only young guy I'd want to see end it is CM Punk. If they had a loser like Sheamus or Ryback end it it would be pointless because who knows if they'll even be around another five or ten years. Ryback is hot now but things can fizzle really quickly in the WWE.
Overall, just leave the streak.