I'm pretty indifferent to Big Mom returing in Elbalf but with the ability to heal and steal souls or use her own, I see no reason why this defeat would stop her permanently. She's not dead, she hasn't reverted back to O-Lin and she failed in her mission of improving her reputation, in fact it's in tatters now whilst Luffy (especially), Law and Kid's will be soaring post-Wano. I don't see why she'd come all this way for Luffy only to stop now when she doesn't seem incapable of continuing another day.
Law's just gaining new abilities whenever and while I like the dude so it isn't as bad as it could be, I wish Oda would simply be firm when he says a character is completely drained or out of energy, not have them just continue in a fight and bust out new moves. It's whatever, I liked the fight, it wasn't as good as a had hoped, but I liked it.