I think Harry being a horcrux is a verrryy possible theory. Either V. didn't know he put his horcrux, or he did it on purpose. I think he did it on purpose. Because then it would make him invincible to the prophecy. The prophecy that Harry would kill him. Harry can't kill V. until all the horcruxes are destroyed. So basically, Voldemort put a peice of himself in the person that was supposed to kill him. And he wouldn't care about killing Harry/horcrux, cause wouldn't he rather end the prophecy with one horcrux less. And who said he can't make new ones either. Maybe he'd rather lose one horcrux, after all, Dumbledore says V can't even feel it when he loses a horcrux.
This is what I think will happen in the final book.
Harry will destroy the remaining horcruxes but fail to find the last one. Dumbledore might already (based on the theory that D. is still alive) have figured this out but he won't want to tell Harry. Voldemort will track Harry down because he will think Dumbledore is dead, and he won't be afraid to kill Harry in the open. Sadly, I think V will kill Harry (but he won't realize that he just destroyed his last horcrux, and he won't even know he is mortal again). Then Neville Longbottom (who will end up being the true Chosen One to kill V, since it was between him or Harry) will come out with revenge and bravery (after all, he is a Gryffindor) and step in front of Vold.. V will probably laugh in his face and won't even bother to raise his wond, cause first of all, it's Neville, second, he still thinks he's immortal, and third, he thinks he just killed the Chosen One. Finally Neville will kill V.. And yeah that's what I think...
Harry being a horcrux
This is what I think will happen in the final book.
Harry will destroy the remaining horcruxes but fail to find the last one. Dumbledore might already (based on the theory that D. is still alive) have figured this out but he won't want to tell Harry. Voldemort will track Harry down because he will think Dumbledore is dead, and he won't be afraid to kill Harry in the open. Sadly, I think V will kill Harry (but he won't realize that he just destroyed his last horcrux, and he won't even know he is mortal again). Then Neville Longbottom (who will end up being the true Chosen One to kill V, since it was between him or Harry) will come out with revenge and bravery (after all, he is a Gryffindor) and step in front of Vold.. V will probably laugh in his face and won't even bother to raise his wond, cause first of all, it's Neville, second, he still thinks he's immortal, and third, he thinks he just killed the Chosen One. Finally Neville will kill V.. And yeah that's what I think...
-Fred