Yes, the prophecy does imply either of them. But once Voldemort chooses Harry, the prophecy refers only to Harry and Voldemort. Hence only Harry will be able to kill Voldemort, because he is the one wizard whom Voldemort "marked as his equal"
(not saying that Neville wont help Harry along the way somewhere, but if Voldemort dies, it WILL be Harry who kills him, I think we can be assured of that)
(not saying that Neville wont help Harry along the way somewhere, but if Voldemort dies, it WILL be Harry who kills him, I think we can be assured of that)