What happens if I beat Ganon in Zelda: Breath of the Wild?
After you beat Ganon the game will reset to the last save before fighting him.
So all your weapons/resources will be returned as they were for that save. The only thing that will change is that you get a star after your savegame or in the menu(I forgot where) to indicate that you completed the game.
Ganon can be fought again if you want with the same result.
(Source is I did it myself)