None of the 15 pictures available on the official site present any town screens. I remember that one of the first pictures for Heroes V presented the Haven town. Moreover, they were quite proud with the 3D features of the town screens (and presented the towns in the first videos).
Various sources claim there will be no town screens, that everything will be visible and available on the adventure map. Even the mines seem linked to the towns and they cannot be conquered without conquering the towns first. The various buildings in the towns will also be shown on map.
In my opinion, this means that they will get rid of the useless 3D town screens. A lot of effort was invested in those screens in Heroes V and it did not pay off. It was just something (beautiful?) that was used only once or twice. Most of the time we treated the 3D town screen like we used to treat the 2D screens in Heroes I – IV.
I suspect that clicking on the castle on the adventure map will allow us to access a 2D screen with nice pictures where we will be able to build / recruit / trade / learn. Also, maybe clicking on the individual buildings on the adventure map, we will be allowed to take actions specific to that building.
I would prefer the effort for building 3D screens in Heroes V style would be spent for doing something else (like a nice new faction).