i think personaly thay shouldn't ever end the streak i think thay should let it go to 20-0 then he retires but if the undertaker was ever to loss to someone at WM it will be the undertaker hand choosen person to beat him i don't see only main event calbier wrestler ending the streak so that would take out
Cena
Edge
C.M Punk
HHH
Sheamus
Orton
he would choose a up and comer to give them that major boost just like Jimmy Snuka did with the undertaker so who would be a good man to end the streak if undertaker choose to end it
John Morrison??if he hasn't gotten to main event status by next year WM could the undertaker choose morrison to end the streak if he chooses
Drew McIntyre??? he is said to be the choosen one by vince but would the undertake choose him to end the streak???
Wade Barrett???yes he has been in main events but he not a main event wrestler yet and won't be til he becomings a singles wrestler instead of in a group that show me he not ready to be main event man
Skip Sheffield??skip is powerful guy and could be a good choose to end the undertaker's steak
Mason Ryan???could it be mason ryan he is big powerful guy and could have that batista like look
but again i personaly don't think undertaker will end his streak