If Pikmin 4 isn't shown at the Direct, I don't know what will. This game has been purposely held back for 2 years now. I can understand that 2016 would've been a horrible time to release it, as it would've had the same fate as Star Fox Zero.
2017 I suppose was too stacked of a year and Pikmin 4 would've easily been overshadowed.
I doubt 2018 will ever have a title that holds up as well as Mario Odyssey and Zelda BOTW, so Pikmin 4 shouldn't have any issues being overlooked. Even if they have a surprise Animal Crossing announcement at the Direct, as long as Pikmin comes in Q2 and Animal Crossing is Q4 (holiday season) there should be no issues. Pokemon (if ready by late 2018) could simultaneously release with Animal Crossing and the sales of each shouldn't interfere with each other. Although again this is purely speculation as there is no telling whether or not Pokemon is actually 2018 and Animal Crossing is just a mild prediction considering all the signs I've examined over the past 2 weeks.