Our last Big Box expansion, Heart of the Empire, was released exactly one year ago from Saturday. Since then we've gotten 1 small box (Tyrants of Lothal) and 4 boosters.
Here's the summary of each year after release:
2015: Core, 1 big box, 1 small box, 17 boosters
2016: 1 big box, 1 small box, 13 boosters
2017: 1 big box, 6 boosters
2018: 1 small box, 4 boosters
Not only has the release schedule slowed considerably, but we had a 6 month gap between when Heart of the Empire was released and when Tyrants of Lothal was announced. The second longest gap was between boxes (release to announcement) was 4 months 7 days between Jabba's realm and Heart of the Empire, but that gap was filled with the Bt/000/chopper/hera/jawa wave, then tyrants came with its own boosters anyway. the 6 month gap between HotE and ToL had absolutely nothing. All the gaps between box announcements before JR were less than 2.5 months, and most were interspersed with small waves.
If FFG doesn't pick up the IA production schedule we shouldn't expect another announcement until around March, which would mean a July release. Our current gap is at 1 month and 18 days. If the production schedule slows down any more, who knows when we'll get more content.