Late last week, Nintendo announced their upcoming Nintendo Direct was postponed. This was due to an earthquake on the Japanese island of Hokkaido, with the company postponing the presentation to respect those affected by the disaster. And as expected, this led to much speculation about when the Direct would eventually be aired. Would it be […] Source
The game came out on 21 December 2017, which was a Thursday.
Tomorrow (13 September 2018) is a Thursday too.
So it could refer to just a game update tomorrow with an announcement in-game, considering Nintendo Direct generally gets announced within 48 hours before it comes out.