My earlier analysis opposing predictions of Dumbledore's death is called into question by the news:

Reports have indicated that there may have been a leak from the printers. Many of the Dumbledore bets have apparently been coming from the town the printer is in. But a couple of things seem sketchy about this. First, apparently there was some leak there in Book 5:

It is thought that much of the latest Harry Potter book is being printed in Germany, following security leaks at Clays during the publication of the fifth book in the series, Harry Potter and the Order of the Phoenix. A forklift truck driver at the printing plant pleaded guilty in May 2003 to stealing pages from the book and attempting to sell them to the Sun.

Would they really go back there to print without some really good assurance there were more security measures in place this time? And publisher Bloomsbury sent an email to MuggleNet saying:

J. K. Rowling has mentioned previously, in various situations, that any rumour, unless confirmed by herself personally, or by her publishers which are, but not limited to; Bloomsbury Publishing Plc, Scholastic Trade Books and Raincoast Publishing, is merely a rumour and should be treated as trivial.

We repeat: The security measures in Bungay are sufficient to ensure the prevention of any 'leaks'.

Sure, this is a sort of standard reply, but there have been lots of rumors, lots of replies like this, and I don't know of any rumors that have been true.

There's also been "a surge of punters trying to place bets on the character Dean Thomas being the half-blood prince of the title". Interesting theory, but here's the catch with it: according to Rowling herself, in discussing editorial cuts about Dean's background, "[n]ow, I don't think his history will ever make it into the books." (Sorry, no direct link, but go to Rowling's official site, then click on the coffee cup ("Extra Stuff"), then on "Edits", and you'll see the info about Dean.) Surely, explaining that he was the half-blood prince would require some history!

Rowling goes on to explain some things, including that nobody knows Dean's real history: his father didn't abandon them like is thought; he never told Dean's muggle mother he was a wizard, but was killed by the Death Eaters after refusing to join them. Rowling says "I suppose in some ways I sacrificed Dean's voyage of discovery for Neville's, which is more important to the central plot."

Now, if the two "leaks", come from the same source, as it seems to be thought, then the Dean leak especially calls them into question. Rowling has never deliberately misled readers, so there's no reason to assume her info on Dean is intended to do so. But it does make him perhaps the darkest horse to be the half-blood prince... and a very bad bet.

Professor Bainbridge thinks that "Dumbledore has got to go." And he's able to cite to London bookies, who apparently agree. But Dumbledore? I'm not so sure.

I like to fancy myself an "expert" on the subject, but I realize that my hyper-jurisprudential take on the books may cloud my vision of the obvious. Still, if I really had to guess (which of course means that I will), it wouldn't be Dumbledore. At least not now. But before I actually hazard a guess, let me say that I'm not too confident in it. Rather, I offer it as an illustration of one of many reasons I think Professor Bainbridge's analysis may be jumping the gun. (I actually think there's a good chance of Dumbledore dying, but I also think it's more likely in book 7).

So here's the guess (as qualified above):

Snape. The man we all love to hate... for now. Dumbledore has been out of the picture in other instances (called away by a fake message to meet with the Minister of Magic, very low-profile for most of Order of the Phoenix, etc.); I don't think his death is required for that reason alone...and certainly not yet. Snape garners a lot of ire from the reader, mostly for the way he treats Harry. Yet Snape commands, for reasons as yet unknown, an uncharacteristic degree of trust and respect from Dumbledore - uncharacteristic with respect both to how Snape is treated by most people and the trust Dumbledore has in most people. The books are nothing if not suspenseful and twisting (albeit everything always makes sense in the end, unlike plot twists in so many contemporary novels), so I expect this one to be no different.

Snape is clearly a lot more important than we have given him credit for, and has put himself at substantial risk with the Death Eaters in Phoenix. I think a possible scenario would be that just after learning why Dumbledore trusts Snape so much, and, in turn, how important Snape is to the Order, Snape is killed. We may even like him by that point. Also, many people expect Snape to die based on his name. I've seen a number of versions, the least-sophisticated, but easiest to explain is simply to read his name as "sever his nape". Rowling's names are of great significance, but I'm not so jazzed about the nape-severing thing reading because Rowling's name significance is generally fairly etymological, not casual. Now, this reading also ties into what many have read as undeniable signs of a beheading of someone in the series. I'm not so certain I buy that theory, but I do think Snape is a good candidate for death, nonetheless.

Back to Dumbledore, I do think (with near-certainty) that we'll find out at least one more thing about him this time 'round: he is an animagus that transfigures into a bumblebee (maybe a cockchafer, but I'm guessing bee). I also wouldn't be surprised if we learn more about Dumbledore's brother, who has already rather conspicuously appeared in the books.