Lis, Rise of Nations, the masterpiece of Big Huge Games, did not went beyond actual history, it simply did not needed it (if you don't know the game, just go for him, you will love it!).
IMHO Dominations is the same case.
And besides, unless you pay real money, there is a
loooong way to Space Age. To medieval to gunpowder age the cost is 1,5 millions gold and nearly a week of waiting. Imagine how much you must play (or pay, if you wanna go fast) to get endgame?
Apart of go sci-fi, I think that the rest of what you said in your last post is a lot more reasonable. More nations, more customization, the ability to mix and match the game as you please, and events. Yes to all that.
Sci-Fi can be done on a
Sid Meyer's Colonization-like spin off.