Just to clear up some confusion: Neither Sony nor Microsoft requires new games to be playable on previous generation of consoles, nor existing games to continue support indefinitely. Developers are at complete freedom to choose which platform and which generation to support, so Frontier is also at freedom to stop supporting Xbox One and PS4 if it turns out that Odyssey can't run on those consoles. There is really no obligation there. What a company chooses is completely up to them, and the only people to judge them for that are the customers, not the platform holders.
So in practice, Frontier has the freedom to choose not to release Odyssey on Xbox One and PS4, only on Xbox Series X|S and PS5, if they declare that it's the only way the console experience can be adequate. Since their "console plans" are completely up in the air right now, I think that's a very real possibility, if they ever decide to develop Odyssey for consoles.
So in practice, Frontier has the freedom to choose not to release Odyssey on Xbox One and PS4, only on Xbox Series X|S and PS5, if they declare that it's the only way the console experience can be adequate. Since their "console plans" are completely up in the air right now, I think that's a very real possibility, if they ever decide to develop Odyssey for consoles.