Vince_B: Yes, this is what the blurb here says. The issue is, it says "... upgrade to Imperial Edition ...". What is the Imperial Edition? Do I already have to have (buy?) the Imperial Edition, since it says '... upgrade to ..."?
The version you'll be getting if you pre-order on GOG.com before August 6 now becomes the extended Imperial Edition, which contains the game's additional launch content: a development documentary video, an extra campaign map, an additional golden skin for your Dragon Emperor, and the game's soundtrack. The pre-order period is your chance to grab the game and all of the additional content for just $39.99.
If you decide not to take the pre-order route and get the game after the release for $39.99, you'll still be able to upgrade your version with the aforementioned development documentary video, extra map, golden dragon skin, and game soundtrack via the additional $9.99 "Imperial Edition Upgrade". Yes, this basically means that early adopters receive $9.99 worth of content with their pre-ordered copy, free of charge, thus becoming the owners of the most robust version of the game available on launch day.