If Houston don't win the championship next year, I'd be more than happy to see Duncan go out a champion again. Not sure if it will happen, as they went fairly injury free through the back end of this season, mostly from great player management.
As for Jame, Bosh and Wade, Wade cannot go to another team, he needs to stay at the Heat for the money. Bosh and James are most likely going to opt out, take minor pay cuts over longer contracts and try to get some more backup players to help out. James may have needed to do everything in Miami, but except for teams like the Thunder, Clippers, Warriors, Spurs and Rockets, he will still be the one and only.
I agree he will stay in the East, where due to rebuilding or terrible management, there are only 3 or 4 decent teams, whereas the West has about 12, with some teams only getting better next season.