She's concerned about the pressure to write more books after the 7th is released, so unfortunately I think Harry has to go. And from what I can gather in the prophecy I think Harry has to die in order to truly get rid of Voldemort once and for all. Remember the horcruxes? I think one of them is in Harry, when Voldemort transferred some of his powers to him on that fateful night when he was a baby.
As for the 2nd character I have no idea, but I have a feeling maybe Neville...
Harry can't be a horcrux because the actions needed to create a horcrux were not done. Voldemort intended to use Harry as his 7th horcrux but when he went to kill him he was thrown from his body. You need a murder to make a horcrux and he did not manage to kill harry. He couldnt have used the murder of harry's parents to make a horcrux and put it into harry because he would have had to of done it before he was thrown from his body. Also Harry can'y be a horcrux because Harry is the only one who can kill Voldemort according to the prophecy. If harry was a Horcrux he would have to be destroyed before voldemort could be killed and then even without horcrux's Voldemort would still be alive and Harry would not be there to kill him.
Sorry im a dork....i've actually had this discussion many times since the last book came out