I don't think it will be as simple unless whatever happens in Elbaf is of ( quite literally ) gigantic proportions cuz getting the final RP should be quite the prize for quite the struggle.....so it's either gonna be something super epic to which you can say ' allright fk it take it you deserve it ' or it will be something different
My theory has always been
Gaben is the man marked by flame. He has the last poneglyph stashed hidden in oro Jackson somewhere. Possibly in lodestar. With the hatched egg creature protecting it.
After the elbaf stuff, shp meet with gaben and they talk and stuff. Then gaben leads them to lode star. But, CG is there. Buggy challenges shp to a davy back fight. With Gaben as the judge since he knows both buggy and the shp.
Cg vs shp for the last road poneglyph, with cg aiming to get the 3 in shp posession as well as robin.
So that way, they have a very tough fight to get the last one too.