But the character (Fury) still exists in a new incarnation. That seems to be done fairly often in recent decades. Rarely is a character simply terminated. And I've read that Jackson had signed a multi-year deal with the studio.
As for Black Panther, he recently appeared in a very successful standalone movie. For that reason it doesn't seem likely that Marvel would want to terminate an opportunity for sequels.
About 1/3 to 1/2 of the characters from Infinity War appear to have been killed off. Nick Fury seems to be one of the casualties.
In the preview of Endgame it is theorized that the black and white characters in the preview got offed.
Now Endgame may have an ending that brings them back.