Although it would be pretty cool to have multiple cities, like San Diego. I think maybe just Los Santos would be suffice, when thinking about LA in real life, it is such a huge city, and personally I'd rather they got as much of it in as possible, as realistically and accurately as possible, while including the surrounding countryside. LA itself is a very diverse city, from the beaches, to the mountains, to the cities and the suburbs, I just hope they get it right, which knowing R*, they will.