Kasdan did not write episode VII though. Its that toy story writer.

There is no guarantee its not going to be another John Carter, or Lone Ranger.

You cannot spend hundreds of millions of dollars on what amounts to a big budget 1930's and 1940's film serial and not have an ability to lose a lot of money. JJ Abrams alone is no guarantee its going to work. Neither trek film bombed but both fell below Paramount's expectations. the prequels were successful but Lucas was involved he is not involved here.

This is not 1977 where the studio loses 10 mil to 15 mil if the film does not break even or bombs.

Disney has to know that not every film is going to be automatically successful there is risk in each venture. The avengers paid off but that was also a huge risk and so have been each iron man film produced.

They expected the Lone ranger to make pirates of the Caribbean success because of Jerry Bruckheimer well it was a turkey film.