This week Studio Ghibli producer Toshio Suziki has been in the US, where he was speaking at an event at The Academy. At this event Suzuki reportedly confirmed that Miyazaki was indeed hard at work on a new feature, and that he would be producing it.
Work on the project apparently began back in July 2016, and Miyazaki had produced storyboards by the end of the year. As for any other details on the project.. we'll just have to wait. As per last year's report, it was projected the new feature could be completed in 2019.
[source 47News via ANN]