I’m torn. On the one hand, I love the ancient civs and would love to see those. On the other hand, setting the game in the Medieval period opens the door for a lot more technologies and military units (i.e. gunpowder)
I’d be fine with the original civs of AoE I, AoK, or AoC. It would be nice to add civs like the Parthians, and some from Subsahara Africa
Andy, why do you hate us Europeans so much? 
I love you all very much. I wasn’t trying to post negatively about you. Just positively about the others. 
Some ancient civilisations such as Greek, Roman and Egyptian have not survived till modern era and some modern civilisations such as British, American, Persian, Russian, Japanese, emerged later but alive even today. Some more popular cultures flashed in-between i.e. they were neither ancient not did they survive till the modern era - such as Aztec, Mayan, Incan, Mongolian etc. And then there are India and China that witnessed both the ancient and modern times. Hence, while the civilisations in the previous versions of the game were good enough, one addition that needs certain inclusion is India and after that any other that you may deem fit. After all, you cannot ignore 1.35 Billion Indians forming 18% of world population having more than 20 widely spoken and written official languages with the most spoken Hindi at 320 Million and the average of 7 to 8 million, each having distinct and ancient history and culture. Even 5 million is more than the population of many other present day countries that AOE already has. So, for the love of AOE, do not miss India in AOE IV.
I want to see some of the civilizations that were around in the time period the game takes place in. Unfortunately that means some nations would be completely missing/historically inaccurate if they don’t cover all ages.
indians -mughal empire
india-Hindu natives & trade surplus on india,quest& search for india
mughul empire…
indian magics,snakes,tigers…,mysteries,special priest power etc
Hard to say if the era isn’t really nailed down yet. The time period itself really does dictate who may be present, given that a lot of favorites may simply not exist in certain eras.
With that said…
2 Japan. Because, samurai.
British (because you can’t have empire with Briton!)
Rome, if we’re going back further in time.
Greeks (ditto)
Byzantium
France
China
Scandinavia
Celts
Persians
Teutons (only because they are my favorite in AOE 2, but really, I’d be happy with any European faction styled after this one. Crusader knights and castles FTW!)
Mongols
The indus valley civilization
kingdom of israel hhhh
I wish This happans 
i want to civilization from cold war era and countries with internal battles
Every nation which took part in WW1
My choice the Turks.
Vikings, Goths, Franks, Britions
Norse* Viking isn’t the best word for them.
Age of empires 4 could be set after post independence revolution ,
Canada, EUA,
British-India,
Brazil, about empire war can be a campaing , or fall of paraguai in War, Cisplatin war
even the civil wars in Brazil could be worth some content in a perfect world. Tchê, the Revolução Farroupilha lasted 10 years, that’s almost Total War content right there lol
Maybe a bit more love to Bolívar too? poor Bolívar, his entire life is one scenario in AOE3 campaign.
after1830, wars are coming to the colonies and new states, wars of independence, and revolutions, "
there is a whole new world of stories about these wars",
the advantage that many were well documented strategy, maps, tatics … .
INDIAN
I would like to see indian civilization in AOE4 with more upgradation,needs heroes like rani lakshmi bai,Tippu Sultan etc,with special black magical abilities
Rome and Greece, with unique units.