If I remember correctly, he doesn't say Harry is the chosen one, he said Voldemort *believes* Harry is the chosen one. Do I misremember?
That prophecy is very vague, and can apply to Neville, as Dumbledore pointed out.
I'm just guessing, of course, but that would be a brilliant twist on the whole series. I'm guessing Neville kills Voldemort in the final book.
"You are forgetting the next part of the prophecy, the final identifying feature of the boy who could vanquish Voldemort....Voldemort himself would 'mark him as his equal.' And so he did,Harry. He chose you,not Neville. He gave you the scar that has proved both blessing and curse."