I do think that it will be a female superhero who fells the final fatal blow to that shrivelled up prune of a bad guy Thanos. But it might be someone other than Captain Marvel. It could be Nebula.

Nebula is very important to the story, and it looks like she knows where Thanos is hiding. Scott Ladewig, the same person who provided a detailed description of the new Endgame footage ...

Thanos is very happy that he did the snap. It then flashes to Tony looking into space and Nebula telling him oxygen is running out fast. Tony starts recording his message to Pepper and then ...