(Semi-spoiler alert. I've read up thru page 553.) How will he get the sword back? I'm thinking the same way he got it the first time - he'll pull it out of the Sorting Hat. (Though I reckon that he gives it back to Griphook in the end, to keep his word, and as a gesture of respect to the goblins.)
It figures that the climax will come at Hogwarts. But what will the unknown horcrux turn out to be? I'm guessing it will be a good surprise, but not something totally new. It will harken back to some tidbit clue dropped years/books ago, and I'll think "Of course, that's brilliant."
But now there's only 200-ish pages left to not only find and destroy the horcruxes and finish off V, but to get lots of questions answered and find out what happens to everyone.