Open world seems to be the way Nintendo want to go with everything now. It looks like it's going to be a great decision for Zelda... and honestly, I'm optimistic about this Mario game, too. Though a lot of that is probably due to the fact that I only associate the word "odyssey" with fucking awesome games where you can possess your own farts.
Zelda's always been open world, though? It's like the quintessential open world game.
The Mario series hasn't got the world, mythology or the protagonist for a move like this. Like, there is no distinct Mario world and that's evidenced by even in the trailer for this game, with the portly one zipping from realistic New York to weird rainbow skyboxes. He moves so fucking slowly too.