NOW that Norman Mailer has passed on, the big question is: Who gets his Legos? The incendiary novelist built a 15,000- piece "City of the Future" with two pals in his Brooklyn apartment - but where it will go next, nobody knows. Our source mused, "Imagine what a one-of-a-kind artistic creation by one of last century's most acclaimed literary figures would be worth at Sotheby's. But how would you get the damn thing out of his brownstone without breaking it up? You could reassemble it by hand, but that wouldn't be quite the same thing as something actually assembled by the master, would it?"