A. Disney just took things over from LA, so its a very risky decision to fun a live-action series because A. Star Wars came into prominence as a movie B. The New Content won't be the same (Yoda-Obi Wan are both ghosts now, Luke might be a old man now, and lot of the real life actors are either old or have moved on to other projects). At this point, they would certainly introduce a lot of new characters, A movie is the safe bet I think honestly.
B. The return on 120 minute content for a movie vs a live-action tv series are worlds apart. Movies make a lot of money for a lot less content.
C. Movies stars and Movie Production houses have a bigger mass appeal and reach than TV ones.