It could be that someone might "come into their powers" (as Rowling has stated will happen) and that that will mean that there's a true seer in the stories. I do think there could be room for a true seer in the series, but I think there's more obvious reason to suspect Neville is the one to "come into his powers" and I think the hints that are being dropped suggest a medium. Of course, Parvati could be the medium instead (I had a couple of people on my friendslist think of Ron, so it could be anyone, really), so I won't claim any canon superiority here.