Michael Arndt has been hired as screenwriter for Star Wars Episode 7, Lucasfilm announced.  Arndt was reported to be the leading candidate for the job after penning a 40- to 50-page treatment (see "A Writer for 'Star Wars 7'").  
The Star Wars treatment that Arndt wrote was actually for all three films in the next trilogy, according to Deadline
It’s clear that plans for the next Star Wars film trilogy were well in motion before the deal for Disney to buy Lucasfilm (see "Disney Acquires Lucasfilm").