Seems the game is near enough done, they're probably just polishing the game.

http://nintendoeverything.com/super-mario-odyssey-development-is-considerably-finished-various-tidbits/

Super Mario Odyssey received a stage show at the Nintendo Switch Experience this past weekend. Aside from the brief bit of footage highlighting Mario’s moves, a few tidbits about the game were also shared.

Development on Super Mario Odyssey is considerably finished, so producer Yoshiaki Koizumi wants people to get their hands on it. But since the release isn’t close, Nintendo didn’t offer Mario as playable demo.

The theme of Super Mario Odyssey is active exploration by players. Naturally, the story is to rescue Princess Peach from Bowser. Mario goes out from Mushroom Kingdom and travels a “certain Earth” with a hat-shaped airship. Players will be able to go on adventures across various countries.

Director Kenta Motokura gathers many ideas from the team to implement in the game and they build each one into a playable form. Then they keep playing those again and again. The team only throws these ideas into the sandbox if they find it to be really fun.

Also mentioned is that Mario has more facial expressions, and the hat is still a secret.

Finally, some stage tidbits:

Desert

– You can enter buildings from doors and explore inside
– You can go and explore a tower and Tokyo Big site-esque building which you can see far away

Forest

– Very well-suited stage for exploration
– They are putting effort into showing nice-looking grass and dappled sunlight through trees

Urban area

– Mario can jump to the ground from the top of a skyscraper
– You can jump and step on humans; you can probably expect what happens when you do that

this games looks amazing... Holiday 2017 cannot be here soon enough!

I need this game earlier than I thought, Mario jumping on people, Rated M confirmed XD

It's clear that they could have frontloaded this launch with a number of titles (primarily ports), but they're spacing it out across the first year. I imagine this is just the juggernaut they wanted for the first holiday season.

It's gonna suck waiting, but it's probably a wise move; the first couple of months will likely be carried by hype and Zelda alone.

lol everyone gonna be walking around town like Otto Von Bismarck.

The hat is a secret? In what ways?
It was shown, different uses were shown and a crazy cap building (shop?). So we actually know and can guess a lot about it. I'd rather have story-stuff and all uses stay secret. But the hat is not a secret I'd say.

Not taking damage from huge leaps is funny. Inbefore enemies don't hurt you anymore but only bump you a little.

I wonder if the no fall damage thing only applies to the city.

Hahaahahahaha. Is there a nomination to "post of the year"?

Maybe he can lesson it with the butt slam?

Fall damage is a pretty important part of these style of Mario games in the past.

It's a young year but I'll take it :D