I mean, yeah. That's the biggest selling point for me, actually.
If you put in everything for the Inner Sea (or buy it when it eventually comes available, whatever) and you have whatever adventure you're running, you can create a new realm to combine the two.
To be fair, though, you're going to have to do some cleaning up when you first import the adventure. The Varisia from Rise of the Runelords isn't going to automagically merge with the Varisia of your Inner Sea, for instance.
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