In the latest issue of Game Informer, the game's producer, and all-round cool guy, Yoshiaki Koizumi said the following about Odyssey's development process:
"It was always planned for Nintendo Switch. We really were considering a lot of the hardware capabilities specifically for this game, and wanted to make the most use of them."
With the various control options available to players within the game, and the emphasis given to using the Joy-Con as a priority, it does make sense that the Switch was always going to be the final destination for Odyssey.
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I know a lot of people believe that among other games, Odyssey was meant for Wii U, and held back for the Switch after it became clear the Wii U was going nowhere; while this is certainly true for games like Breath of the Wild and Kingdom Battle, it seems like Odyssey was planned for the Switch all along. Which makes sense- with Koizumi heading up development of the game and the hardware, he could have very easily been aiming for the new hardware with Odyssey all along.