The kids these days don't really have a clue about the Undertaker except for video games and the little bit of time leading up to WM. They also look at things differently than adults when it comes to wrestling. If Cena were to end the streak but not in a heelish way then his pop would be the same. He'd have the kids and girls cheering him on and the guys booing him.
As for me, I could really care less about him. I could care less about the streak at this point. I think that it has lost authenticity with the fact that Taker only comes in once a year to wrestle. It's like the episode of King of the Hill where Bill loses his TD record when a high school football player tears his ACL and is allowed to walk into the end zone for the record. Taker shows up one night a year to walk into the end zone. Granted, he usually puts on a good show.