This is an interesting topic, not sure we can do it much justice with what we know now. There certainly seem to be a few overarching design goals in mind though:
-The developers definitely want to reduce the steamroll factor in the game. In previous civ games, a quick war with large advantages could result in taking out a dozen cities/a civ in not so much time. With the new 1upt system possibly resulting in lots of defensive/"trench" warfare and other game mechanics, fast conquest seems to be something they want out. In fact, I would say this is even somewhat of an unfortunate necessity, given that they've created some other game mechanics that could result in rather imbalanced wars, specific focus on capital cities and how domination victories work and so on.
-The entire motivations for warfare and diplomacy are seeming shakier, we couldn't really say for sure, but I would also guess they are aiming for more limited warfare, and on the AI side of things, removing general overbearing belligerence. Instead of multiple civs getting into wars for hating each other, as is common in previous civ games and especially civ4 with factors like religion, the purpose of war may be more limited. I'm not sure "fighting over just resources and border tiles" is what I'd really want but maybe it works for some.
Lastly, one thing that's been somewhat missing from previous titles but could actually be somewhat around here is distinctions in the type and effects of combat fought. Expanding options for pillaging/raiding enemy lands, and razing versus occupying cities, is a good thing, as is increasing the importance of levied/militia/drafted troops as opposed to standing armies on the defensive side. Making the city itself a defender is actually a rather elegant solution I do like for the system. It wouldn't have worked in civ4 or non 1upt but I always favored the idea of encouraging more specific, "garrisoned" units in peacetime and all, and cities defending themselves and the results of actual city capture/occupation in civ5 seem to provide some good choices.