If we get a direct in January, what I expect as far as first party is concerned. These can range from a small update, trailer to big reveal.
For reference what we got first party wise in the February direct.
-Super Mario Maker 2
-Marvel Ultimate Alliance 3
-Box Boy and Box Girl
-Smash update
-Captain Toad update
-Yoshi's Crafted World demo
-Fire Emblem Three Houses (focus)
-Astral Chain
-Zelda Links Awakening
We got a good amount of Nintendo first party related announcements. So I expect similar for this first January direct.
-Animal Crossing
-Smash character 5
-new game (2D Metroid, new IP, etc.)
-new game (Paper Mario, eShop title, etc)
-Pikmin 3 Deluxe announced
-XenoblaDE (only if it releases before E3, if not then it will be in a March direct)
-Bayonetta 3
-TMS reminder