That seem very plausible imo but it would really downplay Hells Memories too imo. Which we've barely seen too for some reason.
I do think it will happen though, maybe even fire and electricity as he can use the latter with Thor too?
Kaido seemed to be affected by and afraid of fire I think vs the Scabbards and then when Luffy tried to red roc him again and Kaido dodged it? Luffy made fun of him or so and it was implied at least that Kaido felt pain from it/the fire?
I'm struggling to remember tbh, I need to reread the fights but anyone know what I mean if its true ofc?
But yeah, Luffy incorporating fire seems like a natural and inevitable step up from how Oda has written the sheer abundance and importance of fire throughout, especially this arc ofc! We Fire Force and Flame of Recca now? Lmao. (Also Fairy Tail for Natsu)