This just in - according to the Official Mafia Wars Facebook Fan Page, a "special Mafia Wars Las Vegas mission" will be available Saturday.
Note that this is not Mafia Wars Las Vegas itself but rather a limited time job (think of the Fix the World Cup / Easter / Valentine's day events). There will be a limited time job that is "Mafia Wars Las Vegas themed" along with a collection (probably a time-restricted one like with Valentine's and St. Patty's Day), and a new achievement.
Chapter 2 of Mafia Wars South Africa will be out soon - will post shortly about that after it goes live. Will have info on the new Mafia Wars Las Vegas jobs shortly as well!