If Lucasfilm is this confident where and when filming will start then there must be enough of a script completed to know that Paint Hall studios in Dublin will serve its needs.
We know there’s a pretty good chance Lucasfilm has its lead actor locked down, as Ewan McGregor has been open to returning to the franchise for years.
With no Star Wars currently on the schedule for 2020 and beyond, though several projects have been announced, it makes sense that Lucasfilm is planning something to be filming by 2019, though if the studio is already deciding where it wants to film things, then the project would seem to be further along than we thought.