The way I see it, if a promoter thinks Sapp is that big of a draw in the future and is willing to pay for his "appearance", then so be it. I will never, ever decide to watch an event based on whether he is on the card or not. Sooner or later, and i think it is definitely sooner, US promoters will realize he is not a draw for a US audience.
Now Japan on the other hand...they have this unhealthy obsession with overly large individuals beating up on smaller individuals or groups. Sapp could come out and take a giant shit in the ring and the Japanese would eat it up. Now that i think about it, they would probably pay extra to see it.