See also Dissolution of the Netherlands Antilles.
In a nutshell: Curaçao and Sint Maarten become autonomous and the remnant of the islands (the BES islands) become special municipalities of the Netherlands.
The question is: how should we replace Netherlands Antilles (with country code ISO-3166-2:AN) in the country dropdown of the average webapplication? I can't find any information about the new country codes. Do we have to add Curaçao and Sint Maarten to the dropdown with the country code AN? How about the BES islands?