Scarlett, in my opinion, was a book that didn't need to be written.
Margaret Mitchell herself said in numerous interviews that she would never consider writing a sequel as the GWTW story was concluded and done, as she saw it.
There was actually another sequel written in the 1970s!
MGM, owner of the GWTW book rights and the Mitchell estate jointly commissioned Anne Edwards to write the sequel. Apparently, there was some sort of litigation and the book was never published, although the completed manuscript is said to still exist.
The estate wanted the book in order to maintain copyright security for the characters, as the copyright was due to expire.
Edwards has said her story remains completely in Georgia, focusing on Reconstruction and the aftermath of slavery.