So I think what you're arguing is JKR isn't going to have a new main setting. That there will be scenes at other places (such as the cave and Snape's house was in HBP), but there will be one main base that Harry will be most of the time and that is Hogwarts. If that is what you mean then I'm not disagreeing with you because more than likely he will be at Hogwarts the most in book 7. All I was saying was there will be events that take place in other places besides the normal places.
I don't believe that the horcruxes are located at Hogwarts. I think that information at Hogwarts will, however, lead Harry to where they are. Therefore, he will be spending a lot of time at Hogwarts. This will also help in Ron and Hermione assisting him. I don't know if they will be attending their seventh year at Hogwarts or not (if it remains open which seems likely), but I can't imagine Hermione not finishing and taking her N.E.W.Ts. I think, though, they will leave Hogwarts quite a bit during the book, even if Ron and Hermione do attend.
As for Harry being a horcrux, check out some of the forums on it. Many have brought up some interesting iideas. We really don't know how the horcrux spell is performed, so it's hard to say exactly, but one theory is that when Voldemort was going to kill Harry, he was planning on using Harry's death for his final horcrux (since it was a very important death to Voldemort). Voldemort had the object that was to be his horcrux nearby ready for the spell. When he cast the curse on Harry, it backfired. What if Harry was made the Horcrux instead of the intended object; would Voldemort know this or still believe that the intended object was still made a horcurx? As for the death needed to create the horcrux, Lily's death could have been used as the trigger, even if unintentionally. Voldemort might have realized his spell was a success, and therefore thought it had worked, just with a different death than intended.
It seems to me that Voldemort completely had the attitude of kill Harry, kill Harry until the fourth book. Then he didn't want Harry dead. Maybe he realized that Harry was a horcrux after the Tri-Wizard Tournament. Then his attitude changed. I'm not sure about this part cause I would need to re-read the books to be sure, but others have claimed that this was the case. Anyway, it's an idea to ponder. I don't hold completely to it, cause I'm not sure, but it sounds possible. I guess we won't really know till we read book 7.