Depends on if sizes are in high demand from my patrons. But currently I'm satisfied with the current sizes. (Also I can't even think of an NPC that would have bigger than giant.)
That doesn't change my view on it. I currently have no plans to add a bigger size unless my patrons deem it so. If one of them requests their NPC to have a bigger chest size than what's currently available, then I'll add it to the game through their NPC.