I don't see the series changing locations, but I could see Harry inheriting Eb's place in the Ozarks. I could see Harry visiting that place in a single novel and perhaps using it as a safehouse for another character. Yes, Harry's new home is a fortress, but there might be a situation where the character Harry is working with can't be seen entering Harry's home.
The series doesn't have to change locations for Harry to get his inheritance from Eb. Though in a sense the series has changed locations and sort of returned from where it started. With Changes, Harry's cozy basement apartment burned up, now he is returning to his lab with a castle on top of it. Perhaps because the island, the apartment, and Arctus Tor just didn't feel right as home... Not sure the castle will either.
As far the Eb's journals and all of the older ones go, I don't expect Harry will get the opportunity to read through all of them. However, Ebenezer's personal journal might be something Harry will get a chance to look through. One thing to keep in mind is that Jim won't want to give Harry too much information, because that equals too much power. Perhaps Eb's journals will be damaged before Harry get's the chance to read them and Harry will only be able to derive clues from them, rather than complete explanations. Also, I could see the earliest journal, the one that supposedly was written by the original Merlin to be mostly unreadable with only a few words or symbols clear enough to make out, but perhaps just enough for Harry to learn something important from. Most likely, only Bonea would be able to read them as they wouldn't be in modern English and it would be older than even Bob would have experience with.
I think it is vital that Harry get those journals, especially the early one that Merlin wrote if they can be translated.. I believe there are clues in them for the coming BAT that no one knows of, or if they did, would fill Harry in about. Even Eb came with this "need to know" crap in Peace Talks and then told Harry he didn't need to know about his own life at this point! Listens to Wind may be able to help.