Odd that you mention 30 years ago.
How soon they forget. Backstairs at the White House (1979), was an excellent mini series staring primarily Black actors. Watched it in school and it certainly made enough of an impact on me that I immediately referenced it. So, yes, its been done before and it will be a heck of an act to follow.
In some ways it could be a sequel of sorts given it starts during the Presidency where this one ends. I would hope with a cast as good as this that they have a script that will do the story justice.