Kane never said if he won it (the title) he'd slip up and only hold it for one day.
The sources have said that when asked about the title Kane has said it's time for the younger guys to shine. However, the sources don't point out who asked this.
If Vince came to Kane and said we want to put the title on your for a couple months, Kane wouldn't say no. Just on the principle that he's been so loyal to the company and has done whatever they've asked, he wouldn't say no... especially if it meant putting over one of the young guys he's talking about when he has to lose it.
That's just a dumb statement and nothing like that was ever said.
I do remember as well reading that Vince and various others backstage believe it has bothered Kane that he was never given a real title run.
So continuous crappy storylines, misuse of his character, coupled with a bad knee that won't get any better... Kane's probably not very happy wrestling. Maybe Vince should give him a reason to be.
As far as Kane going to Smackdown! to team with Taker... I know the source said Kane requested it, but I don't want to see Kane go his whole career with such a crappy reign. Another Taker/Kane fued really does nothing for me. They've done it so many times in the past. Another Taker/Kane run together does nothing for me because all of them inevitably end with Kane turning on Taker and Taker kicking his ass for it.
Besides, Great Khali will not be around much longer, no need to waste Kane's push on Smackdown! being an accessory to Undertaker's fued.
If Kane gets to win against Batista (or whoever) for the World Heavyweight Title, so be it, I'd love it. Anything else at this point of his career is just a waste of time. He is one of the guys that's been in the ring with everybody. He's been in there with HHH, HBK, Stone Cold, the Rock, Batista, Undertaker, Angle, RVD, Jericho, Big Show, Edge, etc. He's wrestled and has had fueds with every big name possible, both actively in WWE and retired from WWE.
The only major superstar he's never had a fued with is Cena. But still, that couldn't last more than a little, unfortunately with Cena going over.
