When this months Game Pro came in yesterday it said that the cities were not the size of Vice City, as a matter of fact the city of Los Santos is four times the size of Vice City.

Game Pro Magazine: September 2004

Quote:
The city of Los Santos alone is fur times the size of Vice City, which is pretty scary considering that their are two other cities and even larger deserts and badlands connecting them for you to explore.

Voice talent and licensed music is not yet finalized, but you can expect a glitzy announcement coming in the next few weeks...
Pick up September 2004's Game Pro for the whole article or it might be avalible online. I'm not sure though...