If you currently own Total War: Rome II, you'll be happy to know that you'll be receiving the new expansion for absolutely nothing. On September 16th, Total War: Rome II Emperor Edition will be released and all current players will be upgraded for free.
The new edition will include the Imperator Augustus Campaign Pack DLC that covers the events of the 2nd Triumvirate War that was ultimately the death-knell of The Republic. The Emperor Edition will also be comprised of numerous improvements to the base game including overhauled building chains, a redeveloped politics system, and all free content updates since the game's launch in September 2013.