Just a thought that crossed my mind in these days: I have a feeling Animal Crossing is further than most of us think/hope, many expect to see the game next year but I don't think that's the case. Next year seems to be packing a bunch of releases that have been announced/teased for a while counting the new Yoshi game, Fire Emblem: Three Houses, Pokémon's new mainline game, likely Bayonetta 3 and Retro's new title and possibly Metroid Prime 4, I don't think this to be the full lineup, but I also don't expect any other heavy hitters (unless they are new IPs/third party titles), just other Nintendo titles that sell moderately well like Pikmin.

Most of the staff that is involved with Animal Crossing is also tied with Splatoon 2 since the same team created the two games, while it's likely that Nintendo begun the process to split the team in order to enlarge their software output as well as allowing developers to focus 100% on both of these important IPs I think there's been too little time to form two completely independent teams, leading to development for the new Animal Crossing game being slowed down by the constant updates Splatoon 2 will keep getting for another whole year.

I'm sorry Animal Crossing fans, let me know if you disagree, I'd be happy to be proven wrong

You are probably right, i don't dare to guess after being so sure that AC would be coming this September

It'd better not release later than 2019. This is already the longest wait between Animal Crossing games, and if it doesn't release by March 2019, it'll also be the longest wait between a console's launch and its Animal Crossing game being released, excluding N64 for obvious reasons.

The AC/Splatoon team hardly needs much more development time at this point. They already have tons of HD assets from amiibo Festival, Pocket Camp, and Mario Kart 8.

Also, your proposed lineup without Animal Crossing would be even weaker than what Nintendo has this year. At least in 2018 we're getting 2 games with 10M+ potential. It would be ridiculous to only have one such game next year, especially since it would mean relying on Pokemon two years in a row. That's not to say Nintendo wouldn't do something like that, but still. Ridiculous.

I could see it in 2019 or 2020. No other year really. So this prediction is a bit tame. I wouldn't be surprised if they tried to make a new Mario game like a New Super Mario Brothers but rebranded for 2019.

Nah if there is no 2D Mario coming out in 2019, Nintendo would only release one big selling game that year….. I'd still believe we will see it in around summer 2019

I hope you're wrong. It's been too long.

Who knows, maybe they’ll surprise us and announce it in the possible September Direct and release it in march 2019.
I know that won’t happen, but like I said, who knows 😁

I'm not going to write a 2019 release off just yet. Reggie said there would be more to show this year, some of which would actually be releasing this year, which will give us an idea as to what their 2019 will look like. If it seems too light, I'd say 2019 is a good bet. I say that as someone who thinks Metroid Prime 4 will be released 2020, and was shown way too early for easy bonus point with their fans during E3, when they should have saved it for this year, right after the Ridley for Smash trailer. I also say this as someone that believed a rumor that Animal Crossing for Wii U was well under way and was pushed to Switch, with some redesign necessary due to things that were planned for the gamepad needing to be reworked. If 2019 is looking light as we head into it, I'd expect a surprise reveal at E3 with a late summer or early fall release, or maybe even a late spring or early summer one if they reveal it in an early 2019 direct.

I think they'll reveal it next year. The Animal Crossing team has been quiet for some time/aside from them being involved in Splatoon, true. and keep in mind Pocket Camp and Amiibo festival were smaller games co produced with ND Cube. But I don't think it'll be released next year. I mean it could but I'm guessing next year is Fire Emblem, Yoshi, Bayo 3, Metroid Prime 4, some sort of Mario game whether it be an RPG, sport, etc. and of course Pokemon Gen 8 with Wii U ports sprinkled inbetween.

Nintendo has options that's for sure, I don't think they'd need it in 2019, so I agree. 

Well, it not seems a kind of game they will announce 1 year or more before it's release.
I think it will appear on a direct 3 to 6 months before the release.
Anyway, we have only 1 10+million seller for 2019. We need other to keep the momentum of switch after the 20 million. So either Mario 2d either AC is a given on 2019.