Thank you for all the incredible work you and the rest of the audio team have done!
My answer to your question is going to be a horrible cheat
It's far too general, but maybe audio in Elite is a victim of its own success... my imagination goes wild imagining all kinds of things when it comes to planetary atmospheres.
Will we hear 'windswept' sounds as we dip into the atmosphere, making it a radically different experience to flying in space? (assume the ship creates the audio cues like everything else we wouldn't actually hear).
Will the sounds of atmosphere respond to the environment? When we fly through clouds, will there be a denser soft-edged feel to the audio? If certain clouds interfere with sensor effectiveness (such as in gas giants), will there be an audio cue? Will atmospheric sounds scale with pressure, becoming 'thicker' and heavier? Will the ship start creaking at higher pressures? I can see big scaling problems with this too, since the variation in atmosphere pressures is huge! How about turbulence and storms? Will the audio change depending on the composition of the atmosphere? Helium, or water? Could that be conveyed by audio?
And then there's 'liquid' atmospheres - could ships be submersible, and how would the audio change when that occurs? That's even more cheating, obviously, since this isn't actually atmospheres anymore. But seeing what games like Subnautica do makes me look at planets with seas in Elite with all kinds of silly ideas.
These aren't actually expectations I have - just curiosity about what might come in the future! What I actually see is a hugely daunting and incredibly involved series of challenges... not just in audio either - for video, imagine in our atmosphere, how the sun turns red as it goes close to the horizon... because as the sunlight comes through a thicker and thicker length of the atmosphere, more of the blue and green wavelength light is scattered away, leaving just red eventually... is it possible to model this? How would it change on smaller planets (where the change in thickness is less), or where the atmosphere is less dense? Or how about if the composition is different, would that affect it? Or what if the sun is a completely different colour? How much could sunsets alone vary on alien worlds?
So the upshot is - good luck, to you and everyone at Frontier... you delivered the whole galaxy and the best spaceship flying experience I've ever had in my life. I'd say if anyone can meet those insane challenges, it's all of you.