Disclaimer:If you have not read the books, but plan to, don't read this post. This is important since I am discussing important facts of the end of each of the books. Save yourself a lot of complaining by listening to me now
Okay, I have absolutely no basis for what I'm about to say, since it's just an idea (and a pretty good one, if I do say so myself). If I were JK Rowling, I would definatly write something like this into the Harry Potter finale.
First of all, I'll explain my view of the end of each of the books thus far.
Harry Potter and the Philosopher's Stone (Sorcerer's Stone)
The ending of HP and the PS saw Harry, Ron and Hermione entering the third-floor corridor and getting past a series of unfortunate tasks to get to the Philosopher's Stone. Which they past with flying colours. Pretty tame though. Some weed that dies by seeing light, flying keys and a big chess board don't really cut it, especially with these cool wizards.
Harry Potter and the Chamber Of Secrets
At the end of this book, Harry and Ron (along with Lockhart) enter the Chamber of Secrets where they almost get crushed and Harry battles the Basilisk...
Harry Potter and the Prisoner of Azkaban
At the end of the Prisoner of Azkaban Harry and Hermione wander into the past to change the present and also try and get around the Whomping Willow and Dementors. Cool stuff.
Harry Potter and the Goblet of Fire
Harry and Cedric get through the third task (with Blast-Ended Skrewts, Boggarts and Riddles [oooh]) and end up in the graveyard, where they help You-Know-What You-Know-Who.
Harry Potter and the Order of the Phoenix
In The Ministry of Magic they battle the death eaters. Pretty neat for a bunch of kids.
Similarities
From how I see it, these things have a few common aspects. One of those is the fact that JKR tends to find new scenery for the "final showdowns" of the Potter books. The first 3 take place in Hogwarts exclusively, and the last two take place outside of Hogwarts.
Another thing they have in common is that they involve challenges (on the most part, though I wouldn't call the ending of 3 and 5 a real task-orientated challenge, they were challenges none-the-less).
The final thing they have in common is the alternating between people involved in the finales. First of all, you've got Harry, Ron and Hermione. After which it's just Ron and Harry, then just Harry and Hermione, followed by just Harry (and Cedric, if you want to count him) and, finally, you've got the three of them and Neville, Ginny and Luna.
And now... for the point
Going all the way back to book 1, when Harry's wondering where all of his money is coming from Hagrid tells him Gringotts - the Wizarding bank. He adds there's no safer place, besides Hogwarts (paraphrasing there, but you all remember what he said)... yes, no safer place indeed.
One of the safest place in the Wizarding World then gets broken into by someone seeking the Philosopher's Stone, and we can only help but believe that person was Voldemort (which is pretty darn obvious, but anyways...). We all know that Gringotts is run by the goblins (who are ruthless)... and if I remember correctly they were totally stumped by the break in.
Or were they?
What kind of personality traits do these goblins have? They're vicious, cold characters... and as such, I have a feeling they could be bought. Even the dementors have their price, why not the goblins too?
Which brings me to my point: the 3rd floor corridor, the chamber of secrets, the third challenge in the Goblet of Fire... these challenges are nothing compared to what would happen if Harry had to get in (or out) of Gringotts. This leads me to conclude either one of two things: either the goblins will be allowing Voldemort to use Gringotts to run his Death-Eater operation, or Harry will be put away in Gringotts and left there to rot (that would be very James Bond of JKR, not to kill him though).
If either of these scenarios is not to be coming, I am starting to get a feeling that Gringotts will become a pivital part of the story's ending. First of all, why does Hagrid compare the two in the first place? Sure, they're both safe (which is questionable in both counts), but are they comparing something else? Hogwarts representing the goodness (and education) while Gringotts may represent evil (and a hunger money). We all know which the Weasley's value more, and (in comparison) which the Malfoys value more. So it stands to reason the Malfoys, the money hungry family (and a family of You Know Who supporters), may have a certain relationship with the goblins who run the bank...
Enough already gaboman, shut up
A lot of this is way out there, but one idea I've really come to think of a possibility: Gringotts is quite possibly the setting for the final moments of Harry Potter.
Wow. I think Grant is totally on to something here. Points to support this theory.
1. Professor Binns is constantly lecturing about Goblin rebellion
2. Bill Weasley said we don't know who the Goblins will side with
3. Quibbler articles all talk about Fudge hating the Goblins
4. Using Gringotts would involve those high speed carts and would make for an Indiana Jones type ending.
Awesome thread Grant... and that post just rocks! Great ideas and points!
I think that there will be something to do with Gringotts, because there are just too many times that comments are dropped about the Goblins, or about how safe that place is. There is something building up...
I'm holding out for a climax in Azkaban in either of the next two books. It's a location that the reader hasn't actually been brought to, and an action sequence on a remote island could be atmospheric as well as just plain cool.
How about something happening on Pivit Drive? I know that Harry is protected in the house... but, what if there was a way to get around that spell, and there was something huge that happened there?
That would be really hard because there are people from the Order there, plus who knows what type of spells that Dumbledore did to also protect Harry. OH, how fun it would be to see Petunia, Vernon and Dudley cowering in fear, begging Harry to protect them.
Well if everyone here is talking about where the end will take place in book 6,then I should say that it will probably take place at the Burrow.I am thinking that the Malfoys hate the Weasleys,and that Harry likes to be there.Also Harry faced challenges within Hogwarts,outside Hogwords,on Privet Drive(the dementors)at the Ministry of Magic,a cemetery and in Hogsmade(the house were Lupin went when he transformed int a werewolf).Further more Azkaban is being described as an evil place so I think that if there will be a "trip" to Azkaban it will be in book 7(the triangle prophecy)
The only way for Voldemort to get into the Black house is if Dumbledore tells him the location. It is protected. Dumbledore is the secret keeper, so only he can reveal the location.
Sirius Black was the Potter secret keeper... he was the PERFECT secret keeper, but he still wasn't the REAL secret keeper. And, also, I believe they said they asked Dumbledore to be their secret keeper at one time, but he declined. Perhaps there's a reason behind that. Perhaps he's got a big mouth and can't keep a secret.
The writing on the paper was from Dumbledore AND Dumbledore said that Kreacher could not tell any secrets about the order because he was not the secret keeper, Dumbledore was. Grant, you brat.
I don't know if we'll ever see Azkaban, but I really do think Grant is onto something with the goblins. Good thing Hermione pays attention is History of Magic class.
Wow. I think Grant is totally on to something here. Points to support this theory.
indiana jones style ending sounds good to me! But it wont be as exciting to read as it will be to see on the big screen, I think.
The Burrow would be an unexpected place to have the story go. I like it. 
Grant, you brat. 
err... Snape!
I'm sorry