I just realized something about the structure of the adventure packs that I hadn't realized before: Because FFG has to make each adventure pack independent (requiring only the core set as a prerequisite), there can't be any mixing and matching of encounter sets between the adventure packs. For example, if Adventure Pack 1 introduces a new encounter set, that set can't be used in the scenario for Adventure Pack 2. So every adventure pack will be limited to mixing only its own encounter set(s) plus the seven encounter sets in the core set. That's kind of a bummer for me.
I'm still trying to figure out what that means for the structure of the adventure packs. I hope it doesn't lead to a lot of duplication and reprinting of encounter cards between adventure packs.
I was also hoping that future adventure packs would introduce new cards to add to previous encounter sets, to give older scenarios additional replayability. Looks like that could only happen with the core encounter sets, though, if they do it at all.