OK, so here’s the sequence of events so far. Lawrence Kasdan and Simon Kinberg were first announced as joining the Star Wars team as consultants on The Force Awakens and writers on two untitled standalone films. Then Michael Arndt got moved off The Force Awaken and Kasdan stepped in to write the film alongside J.J. Abrams. Meanwhile, Kinberg became a writer and Executive Producer on Rebels. Outsider Gary Whitta was then brought in to write the first standalone (which is to be directed by Gareth Edwards), and has now exited, with Kinberg rumoured to be completing the writing on the film. (Kinberg was previously expected to be writing the second standalone, which may or may not be directed by Josh Trank.)
This looks kind of chaotic from a fan’s perspective, but one thing you need to keep in mind is that these are not auteur films like Star Wars under Lucas. These are studio films, and Kinberg in particular seems to be part of a team including Kasdan and Kathleen Kennedy who are brainstorming these films and hiring people like Whitta and Gareth Edwards to do the grunt work to get them made. This is closer to the way a TV series is made than an auteur film, and that paradigm may be confusing some people.
The quality of the product is what’s important, and we’ll find that out in under two years when Edwards’ film is released.