Well, Orlais is a pretty huge place if I'm reading the map correctly. There's room there for plenty of different types of environments.
Producer Cameron Lee shared some details via Twitter during the panel yesterday. Cinematic Designer John Perry said that he's had a longer pre-production on DA3 than any other BioWare title he's worked on Perry: one level in DA3 is as big as all of DA2's levels Regarding the castle from the concept art link above, Laidlaw said: "you *cough*... may or may not take control of it" Laidlaw: customization is going to be bigger than DAO (followers, etc.) Laidlaw: "it feels wrong to not have a 'little' Flemeth in your game *grin*" David Gaider: Playable character backgrounds "will have significant impact on the story," despite not being playable Regarding DA2 companions: you may see what happened to some