But it's like you said, with time and a well respected actor, some of those against recasting could have possibly been won over. The movies is at least 3 years away. Plus a very good performance, while it may or may not rivaled Chadwick's could be good enough to sooth some of those fans.
Not recasting means no T'Challa. There's no way they are going to win over fans of T'Challa with a Black Panther II and no T'Challa. What is the appeal for those of us who wanted a recast? Shuri? Ramonda? Okoye? None of these characters could have been in the 1st movie and we still would have went to see it because of T'Challa.