It all depends on how they plan to implement a lot of the features, but there are some really cool ways to do city builder type games multiplayer.
One example is how they did multiplayer in simcity. While the most recebt iteration was far from perfect, and its implentation was poor, the basic premise of how they did multiplayer was probably inexpensive to implement and was a really cool way to allow players to interact without sacrificing the singleplayer aspect of the game.
If when you start your game you are given an entire "planet" and you can implement colonies on different parts of the planet, it would be really fun to be able to specialize and trade with the other colonies, compete to reach goals, help each other in disasters, and compete for resources. It doesn't have to be a war game to be interesting.
Another advantage to that idea is how you don't neccessarily both have to be online at the same time to play together, but you still get to interact. I lived being able to play with friends across timezones, check each others progress, etc.
On the flip side to this, it would also be cool if you simply shared a colony and both worked to manage the same colony cooperatively. It would be more difficult to keep interesting and more difficult to implement, but I am hapoy either way. I just hope for a way to interact with friends in this game. For me multiplayer is essentially a requirement.