Victoria Alonso gave an interview to an Argentinian journal. She didn't give any spoilers, but concerning Black Panther II she said:

- What's going to happen with Black Panther II? There were talks about creating a CGI Boseman...

No. There is only one Chadwick, and he's no longer with us .Unfortunetly, our king is dead, not only in fiction but also in real life. We are taking our time to think how are we going to cotinue that story and what are we going to do to honor this chapter and this unexpected and terrible death. In production, sometimes two or three months are enough, and you say time has pass. But this is not the case, we need to think what are we going to do, how are we going to honor the franchise.

She's claiming that they didn't make a decision at this moment. But the comment about "dead in fiction" might be suggestive that they are not considering replacing the actor.