In other posts, the elemental associations of the houses, and the colors JKR associates with the houses and elements have been outlined - I believe we will see a parallel association with the 4 remaining Horcruxes. Harry and Dumbledore named two of the items: Slytherin’s Locket and Hufflepuff’s Cup, and additionally the snake Nagini has been named as a likely horcrux. I don’t mind being led by the nose by the author. =)

I see a sort of association grid:

Earth Hufflepuff Yellow/Black Cup
Air Ravenclaw Blue/Canary ??Ravenclaw’s something??
Fire Gryffendor Red/Gold Snake?
Water   Slytherin Green/Silver Locket  Underground Lake

You see that I assume the water association with Slytherin and the locket was reflected in the location - a lake, in a cave, at the ocean. What do I think this means for the final volume of the series? I’m going to let my guesses take over here.

The locket: I gues I buy the “locket is at Grimmauld Place” thinking and believe Harry will realize this and return to the house he inherited form Sirius. I expect this to happen sometime after school has resumed at Hogwarts because of the following plot elements I expect to play into it. RAB, as many many before me have speculated, is Regulus Black, and, to paraphrase what I’ve read - I can’t remember where now - that he penetrated the lakes protection similarly to Dumbledore with Harry as a helper - he took Kreacher as his helper - Kreacher who didn’t register as a wizard in the boat the same way Harry didn’t register. Regulus then compelled Kreacher to drink the noxious potion so he could retrieve the locket. Someone - Ron, Harry or Hermione, will think of RAB being Regulus and Harry will summon Kreacher and learn this story (or perhaps he will learn legilimancy and use it as DD did in his search). Learning what happened, he will want to know about the locket, which Kreacher will have squirreled away. Unless mundungus stole it. hehehe

I don’t think this is the first one we will see however, I believe that will either be the air or earth horcrux.

The air horcrux, the something of Ravenclaw’s whatever it is (for some reason, lots of folk seem to gravitate towards it being a tiara). Just as the water horcrux was hidden in the middle of a body of water - I expect the air horcrux will be hidden in - the air, either at a remote mountain peak (I think this is the more likely possibility) or in an enchanted floating place (how fun would that be?). In either case, Harry will need to use his broom flying/quidditch skills to make it through this trial. I also expect that this horcrux will turn out to be guarded by (a) dragon(s). Not the baby, we saw in book one, which prefigures bth the one in book 4 and the one I postulate in book 7, not the mother dragon, powerful and dangerous though she is, but an ancient, uber powerful grand stallion of a dragon (what are boy dragons anyway?). Will Harry have help? I think he will - from not only Ron and Hermione, but also from Charlie Weasley, Viktor Krum (flyer extraordinaire) and perhaps from some others.

The earth horcrux - Helga Hufflepuff’s Cup, is associated, by virtue of its earth element, with wealth, a clue that leads me to think this one is hidden - well not qutie in plain sight, but perhaps somewhere we have heard of so often and haven’t given too much consideration - Gringott’s Wizarding Bank. As Hagrid says, “nowhere better to keep something saf than Gringott’s, except for perhaps Hogwarts, because you’d have to be crazy to try to steal something from it. We know from book 1 that Voldemort somehow has access to the Gringott’s underworld - I don’t begin to speculate - but I think this is where the goblin I mentioned believing will come into the story (in the Magical Friends post) makes his appearance. Besides Ron and Hermione, who else might help Harry - I’m drawn to the goblin, Bill Weasley (Gringott’s insider), and - yes - I think he makes a return - Ludo Bagman (his yellow and black striped Wasps uniform is too obviously Hufflepuffy for me to ignore).

Assuming these three are plausible, that leaves the Snake Nagini - Snake/Slytherin should be tied to water but I think Harry is likely to encounter Nagini and voldemort at the same time, in the final battle near the end of the book. Fire will appear as a set piece or an environment for the last of all battles we will see in the series. I’m not sure I beleive it will happen at Hogwarts, as lots of folks sugest, but I do think it will be a battle royale with ust about every good guy we’ve ever met and lots of fair to middlin ones as well in a rolling 3-5 chapter festival of spellwork winnowing down from a big crowd to a select few, which will include besides Harry, Ron and Hermione, the other 3 scrappy fighters - Luna, Ginny and Neville, an assortment of Order of the Phoenix members and - at the last - Fawkes who will replace Hedwig (after Voldemort has killed her) as Harry’s pet and emblem, symbol of his new role as rightful leader of the Order of the Phoenix.

Some further notes on people in their archetype - the colors and elements I’ve named above lead me to assign archetypes to a lot of characters - after re-readeing the books too many times. I’ll include that as an annex here. I want to emphasize that I believe a lot of people are sorted into houses which are different from their archetypes, but their archetype shows through. (I don’t mean for this to be exhaustive but it focuses on the characters I’ve been thinking appear in the horcrux battles)

Gryffendor, Red/Gold, Fire: Ron Weasley, Viktor Krum, Ginny Weasley, Hagrid, Fawkes
Ravenclaw, Blue/Canary, Air: Hermione Granger, Fleur DeLaCouer, Firenze, Fred and George Weasley, Madeye Moody
Hufflepuff, Yellow/Black, Earth: Neville Longbottom, Ludo Bagman, Molly Weasley
Slytherin, Green/Silver, Water: Harry Potter, Luna Lovegood, Dobby

How’s that for some crazy thinking?