This providing, if, or rather when CIV 6 comes out it will give us what we, the progressive civ fanatic folk out there need, and that is when playing as a particular civ we will without any doubt feel that this is our civ, in accordance to the way this civ started/developed and progressed in real history, it's unique buildings, great people, abilities, units, ideologies, wonders, technologies, city building styles, city names, as well as possibly other unique details of the civ we are playing as we continue forward in history, with each passing turn. This way every other civ will look and look and behave somewhat to drastically different, every time we encounter one.
For example:
I play as Russia, I can expect to be able to build not only the Cossack cavalry down the road, but, among others, also the berdiche wielding Strelets musketmen, Russian axemen, Noblemen Cavalry, Kreposts, Mig fighters, T-34 tanks, the fearsome Katyusha's, Orthodox Christian churches and monasteries and the Kremlin. I can also expect the birth of Lenin and a very rewarding acceptance of communism as my temporary government of choice, providing me with greatly improved military unit production, the KGB, perhaps other incentives, but as democracy proves itself superior through economic and human right means I might/will be forced to adopt it as my government type. Let me hear the Russian music and songs throughout the game, let me hear Tchaikovsky and Kalinka, the song(among others). Let the available leaders of these people be expansionistic, spiritual, scientific and militaristic, among other traits, just like they were in reality, or let me pick my own trait bonuses, name and appearance, to feel that I am leading my tribe, but as myself, not a historical figure, let's see how will I lead them?
Let us feel that we are actually guiding these tribes, each of them with different pluses and minuses, their own unique units, buildings, abilities, languages, city/people names, and so on. However, give us their roots and the uniqueness/flavour they in reality developed throughout their history, give me this stuff and I will never stop playing Civilization, the game.