Sounds (and looks, oh good looks) amazingly cool, but I could spend all night fanboy-ing out over it without substance, so I'll instead address some issues that jump out at me, that might (note: MIGHT - like the rest of you, I have yet to see any of this in action) be not as awesome.
In order to avoid a senseless shitstorm I'm gonna move the end-of-post disclaimer up to the front:
But despite all this, the game does look awesome, and no doubt it will be tested and tweaked to as close to perfection as a game can be. And we'll just have to see about the actual effects of all that I've mentioned here, so basically, this entire post is theoretical.
And one more thing: Units not dying after combat? GLEE! I love it. I've been waiting for this for so long.
Right. Now on to the issues.
First off: no stacks. Bear in mind that I've never played any Civ multiplayer, so the only mega-stacks-of-doom in my games are my own (or buildups of workers or outdated units or aircraft or etc. in a city). It's certainly very interesting, and I'm sure it'll work wonders with terrain and positioning and such, but banning stacks outright? Wouldn't this make combat more tactical than strategic? In the older Civ games, a unit on its own could be taken to represent a brigade or a division, with a stack or a close group of units being an army, preferably with a combined-arms aspect or simply a fuckton of cheap cannon-fodder. Now, a single unit would represent that army. You'd lose a lot of versatility, and combat would be a LOT more one-on-one, which admittedly sounds good but which also means that any gathering of more than two or three units - which is pretty much mandatory; say one core combat unit, spearman or other anti-cavalry defender, cavalry/armour corps, and that's without catapults/artillery, archers, specialised units, etc. - will spread out over a huge front, and any serious war will take up a massive amount of space, space that you might not actually have - turning what is, in theory, an epic fight between superpowers into a giant traffic jam where only about a quarter of the units involved are actually fighting. This kinda puts the kibosh on human-wave tactics, even when they'd be legitimate and not just "look at me spam 3 of the best unit in the game every turn!" matches. And let's not forget the implications for naval combat. Any kind of serious navy will take up a space the size of the North Sea, and a full-scale naval engagement - even one battle - will require roughly the Atlantic Ocean to work. I hope that this field remains open to modification. I know I'd want to play - perhaps even make - a mod that implements this to a somewhat limited degree (say, max stack of 2 in a forest or hill, 3-4 in a plain). Nonetheless, it's a fascinating concept and I can't wait to try it out.
Second, ranged fire. Archers firing two hexes away. Now we had units that did this in Civ III, and mods for it in Civ IV, so it works, but if Archers can fire two hexes away, wouldn't that give them about the same range as a tactical cruise missile? Or is the combat done differently, on a smaller hex grid than the strategic map? Because if an ancient-era archer using a creaky bow can shoot clean over a city and the hills beyond it to hit an enemy, I'd like to see what "modern"-era (because in its own time, every era is the "modern" era - one day even this era will have a name. My money's on "The /b/tard Era") howitzers can do. Maybe they can shoot all the way across a smaller ocean. No, but seriously. I'm all for ranged attacks, but if Archers can shoot two hexes already, what about artillery? They simply can't be limited to a bow-shot's distance or it'll just seem ridiculous, but you can't increase their range all that much either or they'll become the equivalent of a conventional intermediate-range ballistic missile. What would be interesting is if this means that hexes are smaller than tiles in older games, so for instance a large city would span multiple hexes. Of course, I sincerely doubt that's the case, but that'd make for some interesting games. Or at least an interesting mod.
Thirdly. Only one iron unit per iron resource? Well, like others have said before me, chances are that this means that the presence of resources is increased. But if it doesn't, this could have some serious implications. Yeah, it'd fight the mega-stacks-of-doom, but at what cost? You wouldn't be able to build up a serious army, or you'd be forced to branch out to other, perhaps less useful units to fill out your ranks (whereas swordsmen are traditionally a general-purpose unit, spearmen, for instance, are mainly useful against cavalry - but what if the enemy doesn't have horses?). And if you choose not to, your units will all be useful, but they'd be spread extremely thin, and if you're fighting on a land front of any kind of size, you're gonna be bypassed left and right by units that would basically serve as little other than experience generators for your forces (again, spearmen come to mind), but which can now begin a campaign of happily ravaging your countryside. I was going somewhere with this..... Oh yes, I do sincerely hope this means that resources are more plentiful, because otherwise, you might even have trouble maintaining garrisons for all your cities if you expand fast enough. There are upsides to this though, but since this paragraph is long enough already, I'm going to leave those be and move on to the next issue.
Fourth. The leaders. I see a lot of over-the-top phrases here, but reading between the lines, Napoleon's battlefield and Gandhi's cliff seem to be little more than the backgrounds of what used to be the leaderheads, which are apparently now an entire scene. I do think that this overblown announcement means that we'll get to see more than just the head and shoulders (and sometimes hands and wrists) of the leaders (as evidenced by that portrait of Dick Van Dyke in a foul mood - seriously, that is the most un-Bismarck-like Bismarck I've ever seen), but I don't really see a lot more there. You can only pimp the diplomacy menu so much until it becomes needless clutter and a waste of time and space.
Fifth. No more religions? Why? It worked pretty well IMO in Civ IV, gave you a way of improving your happiness, and it offered plenty of openings for modding. Also, the diplomatic aspect worked well - spread your chosen religion around, and you get more influence; conversely, some rulers (*cough*Isabella) will be quick to brand you a heretic and you'll soon have Conquistadores at your borders. And (especially with modding) tensions within your civ could also run high, as foreign religions spread to your lands. And one of my favourite diversions was playing with just one city and researching every single religion first before expanding, thus allowing my capital to be the holy city for all the religions of the world. Fun times. (Also lots of Great Prophets.)
Sixth. Still doesn't look like there's true 3D terrain. Pity.
That said, the city states do sound awesome, and I still stand by my claim that this is a purely theoretical post, and I have every confidence in the abilities of the design team to deliver an excellent game.
For the end-of-post disclaimer, see beginning of post.
OK. I started writing this when the last reply was #14. Let's see how many (dozens of) times I've been ninja'd.