I'm hoping to see roads, farm buildings and their surrounding fields, seasons to be depicted by snow on the ground in winter etc and hopefully weather (clouds travelling over the landscape, casting shadows and dropping rain).
The aesthetic appeal of these features would be enough to improve immersion, but I certainly expect to see fully functional roads; that was an obvious feature missing from the previous games and has been much requested in the past. I fully expect roads to give a speed bonus over other terrain, and for NPC travellers (especially civilians such as caravans) to use them by default.
Fields wouldn't need to have any purpose that I can think of, other than maybe appearing in greater numbers in fertile and prosperous regions, battle maps in these areas to reflect the world map (doesn't have to be in a field of wheat or whatever is depicted on the map, but fields of any type or orchards or farm buildings would make sense). It would be even better if fields could be set alight on the world map, much as villages can be raided.
Seasons could have a great effect, both aesthetically and practically. In winter rivers might freeze in northern areas, possibly enabling them to be crossed which would be of strategic significance. Snow coverage would extend further south during colder years. This should reduce the travel speed and morale of parties and harm the production of the farms in the area. Conversely in spring rivers might be larger due to meltwater (increasing after a winter of heavy snowfalls), flooding might occur (I doubt this much detail will be in the game but it would be great). Flooded land of course would make some areas impassable for a few days and damage crop production. On the other hand prolonged dry summer weather might cause droughts, making rivers fordable in parts and harming some crops (though of course some dry, hot weather is good for most crops), and making troops uncomfortable on the march, thereby reducing morale.
I would be really pleased and surprised just to see weather as I described in the first paragraph; the appearance of clouds and rain occuring on the campaign map, but it could quite easily have practical effects on gameplay. The most obvious one is having battle maps take place in rainstorms. A long storm over an unpaved road might start making it very boggy and thus slow to use, perhaps triggering caravans to use longer land routes or even to travel part of their journey by ship (not that I have a reason to expect ships in game, but as a map feature showing trading ships it would be immersive and simple to do- they are just caravans on the water). A party caught in a snowstorm might suffer casualties or be forced into making camp to survive.
Sound is important too; zoom in close to the coast and hear the soft hiss of the waves, hear them crash against cliffs in stormy weather; zoom in close to fields and hear sheep and cows, go near a farm and hear ducks and pigs, go to the steppe and both see and hear herds of wild horses, ride through a forest and hear birdsong and the hooves of deer as they scamper away; travel up to a high pass and hear the winds; in the winter most of the animal sounds will be absent, but in summer they will return and in addition fields could yield the sound of crickets; coming near a city, particularly one hosting an event such as a tournament or travelling fair, you would hear the murmur of many voices.
A lot of that is probably not going to be in game, but I certainly expect to see roads which are used by the AI and boost speed. I would also be surprised and disappointed if there aren't fields or some other features to make the map look more real. Changing snow coverage and weather are the ones I am not holding my breath for.
