We do intend to release small, free updates after launch, but expansions that include significant new features and content will be charged for separately. For example, our current roadmap is to add (in no particular order):

Landing/ driving / prospecting on airless rocky planets, moons & asteroids

Walking around interiors and combative boarding of other ships

Combat and other interactions with other players and AIs in the internal areas of star ports

Accessing richly detailed planetary surfaces

Availability of giant ‘executive control’ ships to players