First off, didn't Laurence Kasdan have more to do with 'ROTJ' than with 'ESB'? As I heard it, the script was pretty much already completed by the time he had come on board, and he polished off the final draft.
As for Lucas...I think the biggest mistake he made was not directing something before making 'Episode 1'. I think he needed to do something else first, just to get into the swing of things. One of the positive things I can say about Ep3 is that I think Lucas did a great job of shooting it, and decided to loosen up for once. It's a well known story that Spielberg used to taunt Lucas because he would always use static shots, never moving the camera. But what he proves in Ep3 is that he is capable of bringing his A-Game to the table...It's just a shame his writing leaves a bit to be desired, but then Lucas is the first to admit that he finds writing horrible.
I still think he'll get to work directing something else soon. Once the Ep3 DVD is released I think he'll start considering new projects. Yes I know that he has the TV project coming up, but he's just going to be overseeing it rather than being directly involved in the production of it.
As for what he's been doing with his time, well I think that he's been keeping a tight rein over Lucasfilm and all it's affiliates until it's reached a place he's happy with. As he said, he has enough money to fund his films for the rest of his life, even if all of them are failures financially.