You are never required to start a new world as old worlds are ''upgradable'' when a major update hits live. That bein said its usually recommended to start a new world after each major update such as the one we just had because old saves, altho upgradable, have a tendency to become bugged sometimes and not behave properly and/or not display new content properly.
In the end its your choice wether you start a new world or not after each major updates. If you start a new save you are most guaranteed to experience the game as the Devs mean us to, with minor bugs often related to new content sometimes shows but are usually minors. If you keep playing old saves it usually works fine altho if you got seabases built where new terrain is added/modified you will experience problems for sure as in Bases being showed with terrain in them or even sometimes litterally deleted. Its hard to tell exactly which kind of problems you can deal with tho.
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In the end its your choice wether you start a new world or not after each major updates. If you start a new save you are most guaranteed to experience the game as the Devs mean us to, with minor bugs often related to new content sometimes shows but are usually minors. If you keep playing old saves it usually works fine altho if you got seabases built where new terrain is added/modified you will experience problems for sure as in Bases being showed with terrain in them or even sometimes litterally deleted. Its hard to tell exactly which kind of problems you can deal with tho.