With the current Adventure Path being so wildly popular, it's no surprise that the Paizo people are gearing up for another.
Personally, I think its the details that make it so successful. Things like adding lines for the various auras and sounds with DCs, and the campaign seeds and web enhancements are, to me, what made this one really great. That and they had a single overarching storyline that every adventure dealt with, something WotC's Adventure Path lacked.
That said, given that they want the next Adventure Path to be as widely useable as possible, it's likely to be set generically, and not in the Forgotten Realms or Eberron. That said, I personally wouldn't mind seeing something Greyhawk-specific, but even that's dicey, since the "specific" part means using more than just the "Greyhawk-lite" pantheon; it'd mean specific GH cities, people, events, etc which can alienate some people who don't have the Living Greyhawk Gazetteer or other GH material. Not to mention it'd mean changing, somehow, a world that WotC has made quite clear they want static. There's also the fact that the recent spate of GH "Critical Threat" articles and adventures (such as "Strike on the Rabid Dawn" "Maure Castle" and the upcoming "Isle of Dread" adventure) may make the idea of a GH-specific Adventure Path somewhat overkill on the GH content.
Simply put, it seems like Paizo will probably give us a generic-setting Adventure Path, but given the high caliber material we've seen so far, I still feel confident that they'll make it top-notch.
