I don't think we'll see extreme weather until they ditch current gen consoles and up the PC requirements. Next expansion? The one after?
It's not just expensive volumetric cloud effects and MS Flight Sim shows how expensive those can be.
With clouds, comes precipitation, bodies of liquid, flowing liquids. This is hard, never been done stuff for a galaxy of planets. It's barely been done for procedural generation in limited landscapes.
With flowing liquids comes the possibility of complex, energetic life too. More development time!