Yes. In one of the Dev diaries (the first one, IIRC), the test game was played on Faerun. Dom:PPP maps can't be used on DomII because the map system was changed so radically (from provinces which consisted of pixels which worked as terrain (AND CHANGED with the scales etc!) to terrain flags for provinces).
I'm not sure about the mods, but I don't think there will be any big chances in the technical side. Additions, yes, but hopefully not too many changes. But if the game itself is changed, then some mods might become obsolete/not work anymore, e.g. if mod replacing Ulm used Black Forest national spell, it should be changed to replace Black Forest instead of Ulm for DomIII. Themes become nations too!
