Another think we don't know is how districts will behave during war (sieges, more specifically). In Civ 5 and CivBE a city was a very monolith thing, shooting as one unit and conversely being targeted as one. But this division in districts raises questions. Will the attacking army be able to target districts individually? Take over some of them, but not the entire city? Will the defending army be able to station forces in individual districts to defend them? When you build defensive structures, will they span the entire city, or only some districts? Or you will be able to upgrade/extend defenses district-by-district?

Historically it would make sense. The walls would surround the bulk of the city, but some part of it would always spill out with time. The keep/fortress/castle of a city would be like a last line of defense, to be taken only after all its districts have been breached. 

What I'm guessing is that districts will be attacked individually, yes. And some may be more difficult to take than others, due to terrain and/or defenses. It would add a strategical depth to sieges, which seems like the right direction in which the developers are going, in general. 

From what I understood from reading the articles, districts can be "pillaged" just like improvements in Civ5, so you really never want to let your opponent step onto them. Pillaged improvements are crippled in some yet unknown way which I imagine could range from greatly reduced yields to complete shutdown of the buildings on in.

I agree that this change will add great strategic depth to the game, both in building your city and defending it from attackers.

I also believe they implied that the military district could defend itself and shoot like the main city, and maybe even produce units itself, making it easier to break a siege.

YEah, I just watched the IGN commentary on the teaser, and it was pretty ... informative :) There they said flat-out that you will be fighting for individual districts in a city. So, that's that. I guess in order to conquer the whole city you will need to first conquer all its districts. 

I'm excited now! All my favorite features coming back (Great Works, for instance)!

I'm fairly certain that capturing the city tile itself is how you conquer the territory. Going for the districts first is a strategic decision you'll sometimes make but not a necessary step to conquest.

Just consider a district hidden behind a city and surrounded by mountains, you would never get to it. Speaking of its making be l me believe that chokepoints are going to be even more vital to frontline cities that you expect to see attacked a lot.

One situation you would choose not to go for districts is against an undefended city you can capture in a few turns with a blitzkrieg raid, saving you from having to rebuild the land.

And yes it does look like they made the decision to make Brave new World a starting point this time, the only thing that I believe wasn't confirmed being back is the ideologies but they might simply have not been mentioned.

In the previous installments conquering a city has been a binary thing -- either you conquer it, or you fail, fall back, and regroup. Conquering or pillaging districts sure sounds like it's going to make a bigger difference than pillaging the old tile improvements. With the hexes in Civ5 conquering cities also became a very crammed action, when you could only fit a maximum of six units around a city -- or more like three, because the other three would be "behind the enemy lines". It sounds like districts would allow for more interesting maneuvers around the city. After all, a city siege should naturally be a wide operation, fought on a large front (and not just three tiles).

Just like in the new bombing runs, you can pillage the districts. 

What usually "spilled out" were the slums... When a city that was potentially under threat by enemies expanded far enough, new walls would be built to cover the newer, vital areas. The only time they wouldn't bother was when a city was far enough from the border to be 'safe'. Although, the Military Districts might account for this.

Also, just by looking at the videos, it seems that simply by fighting on a district, it gets pillaged. Which makes sense, as it accounts for collateral damage from the fighting, especially in modern combat (I'm pretty sure tanks have an unfortunate habit of blowing holes in buildings when they miss, and then you have the effect of bombers carpet-bombing targets).

Still, it seems as the "Districts" are just a replacement for tile improvements. The only real change is in building city improvements on the districts (tiles), instead of in the city itself. Of course, I rarely pilliage tiles, unless I'm not planning on taking a city, or I'm running rear-area raids to take out enemy resources.

Well, at least the Harbor District is very important and not comparable to a tile improvement, as it allows even land-locked cities to eventually produce naval vessels. Also, the Military District might allow you to choose where to spawn your troops, that would be of strategic importance as well. And the Districts compete for space with the actual tile improvements, so you must be careful which tiles to dedicate for Districts and which ones for improvements, now that you cannot just farm (or insert-your-favorite-improvement) everything around the city.

True, its going to make improvements more strategic...  Definately a plus. And I do like the harbor not being tied to coastal cities.

We still need to see how exactly they have implemented the District system. As far as I recall, pillaging specific Districts will yield not only Gold, but also other stuff, depending on the District. If I'm not mistaken, pillaging a Campus will yield Science :)

And then, we haven't seen how exatly pillaging a district affects the city - possibly it will make all buildings in it inoperable, potentially harming city Production and other outputs. This could be potentially disastrous, if used the right way. Imagine, for example, the enemy pillaging your Aqueduct district and causing a Famine in the city. Because there is War, your Builders won't be able to moce around freely, and it could be some time before you manage to repait the district, during which you may lose Population as a result of the Famine. 

Also, I suspect the Science victory will depend on building and maintaining a Spaceport district. What if pillaging it destroys some parts of the Spaceship? This could be a serious setback in the last turns of a competitive game.