The ability to create better weapons will mean that we can probably expect more fighting during this period. Also, the agricultural ability allowed people to settle down, and civilizations begin to crop up. Finally, this section of the game will introduce sea vessels. This period of the game will introduce swords and the almighty Phalanx. During this time, more attention will be paid to medicine, and you can expect this to be reflected in the game.
Armies become more armed and armored.
The introduction of the feudal system will probably be introduced in the game. Also, this period saw the rise of castles, so hopefully gameplay involving these structures will be included. These two factors should alter gameplay in an interesting way. Guns get better, ships get bigger, and science begins to take a larger role in things. Rapid changes abound during this time period.