But that's not Big Mom's wish. This would be a weird ending for Big Mom given how she wants world peace and to get the giants on her side. She is more likely to be a future ally to the Strawhats so her dying here doesn't make too much sense
She's 68 years old she's not going to change, if Oda wanted to go that route he would have done so already.
Kaido's and Big Mom's era ends now, the rest of the story will be about Luffy vs Blackbeard the rising stars of the new era.