Competitive multiplayer also has some tweaks. Your class is no longer tied to your character, so you’re free to use anyone regardless of your play style. You should also see more thematic elements in each Operation (major update).
You might be aware of the technical improvements for the Series X and S, which includes higher overall texture quality and frame rates up to 120FPS. Xbox One players won’t get to opt out of playing against users with newer consoles, but you won’t necessarily be at a disadvantage. The Coalition told IGN that it was improving the latency for the Xbox One version of the game to minimize differences.
All of the content updates are coming to the existing consoles. You won’t have to upgrade your hardware to keep the game fresh, then, even if there’s a clear incentive to do so.