WWE’s storyline explanation for Kane’s injury is that he suffered a broken ankle at the hands of The Bludgeon Brothers at Extreme Rules. We first reported on Sunday that he does have a legitimate injury and he was seen with a walking boot at a campaign function on Thursday. He was downplaying the injury and told a fan there that he would be fine for the pay-per-view. He also said that it was an out-of-the-ring injury.
He is not expected back on WWE television anytime soon and he would have probably taken time off anyway because he is in the middle of election season. According to poll results in Knox County, TN, it is widely expected that he will get the votes to become Mayor.
There is no timetable for his return but he has stated in interviews that he still plans on staying affiliated with WWE even if he becomes Mayor.