I like this line of thinking. We can call Iger and crew a lot of things, but they aren't stupid when it comes to making money from a sure thing. As far as a guaranteed return, Star Wars at DHS is probably the next closest thing to DVC.
As far as the 6 years for Avatar at AK goes, it's apples and oranges. AK had large expansion plots and they can very, very slowly start clearing ground and build without impacting the rest of the park. DHS has no realistic expansion areas unless they build out into the parking lots. The lots need to be expanded if you plan to bring in more guests so they need more parking, not less. Most likely they would be closing some or all of the following: Backlot tour, LMA and Indy stunt show. If they do this they are taking away huge people eating shows and attractions that are suitable for all ages. Many consider DHS a half day park already. Take away 2 or 3 attractions for 6 years and the place will be hurting. It's my pixie dust laced, overly optimistic opinion that whatever they build at DHS (Carsland, MI coaster or Star Wars) it will be built in half that time and open before Avatarland. Possibly as early as end of 2016.