Atmospheric worlds -if done right- are much-much more complex than airless worlds, I think those are at least two years away. My bet is that first gas giants will be opened up.
I think the wait will pay off, but I'm also sure people disappointed with Horizons will be disappointed with atmospheric worlds too.
Wouldn't it be incredible if everything short of Earth-likes opened up as part of the Q4 update, with the gas giants and their associated gameplay being paid content between now and then?
I think you are right regarding Earth-likes being at least two years away, but I think there is a reasonable chance that the rest could unlock this year.
Riôt