From a THR interview with Bob Iger:
So according to Iger, the only person responsible for the speed of release of the Star Wars films is Iger. This slow down is no particular surprise to anyone, of course, but I am still happy to see this choice be announced.
Many believe Disney should pump the breaks and not put out a Star Wars movie each year.
I made the timing decision, and as I look back, I think the mistake that I made — I take the blame — was a little too much, too fast. You can expect some slowdown, but that doesn't mean we're not going to make films. J.J. [Abrams] is busy making [Episode] IX. We have creative entities, including [Game of Thrones creators David] Benioff and [D.B.] Weiss, who are developing sagas of their own, which we haven't been specific about. And we are just at the point where we're going to start making decisions about what comes next after J.J.'s. But I think we're going to be a little bit more careful about volume and timing. And the buck stops here on that.
So according to Iger, the only person responsible for the speed of release of the Star Wars films is Iger. This slow down is no particular surprise to anyone, of course, but I am still happy to see this choice be announced.