It could be via an expansion or DLC but somehow I doubt that...DLC doesn't seem like a route that SD would take (though things could always change) and it has been stated by a dev that the design of the game is not conducive to releasing DLC (though I have no idea why that is)...if it were an expansion, I have a feeling it would be adding a lot more than just 2 planet types and a new shadow system, not to mention we'd probably see more press/info than this...

I'm guessing this is all just part of a very large update, probably the update Yarlen referred to that would revamp the shadow system...