Unturned 4.0 will be mostly an apocalyptic game, and I do think the landscapes and ambiance will be the most important thing, maps shouldnt look like nothing happened, Seattle, Moscow or other 3.0 cities look intact, while it shouldnt be that at all, with the event of an worlwide outbreak, there would be riot ( burned cars, destroyed shops ) , attempts to protect a state peoples ( large quarantine wall, huge military presence ) and major strategic / infected area ( cities, airports ( take à look at Donetsk airport, sadely, it is Exactly what an apocalyptic airport could look like ) and highways ( in an attempts to stop the infected, bridges would be blowned up, interchange too and same for tunnels, we could also see many military checkpoints ) .
Some areas could also be whole ruins, imagine a city that was bombed, there wouldnt be any glass in building, there would be craters on the roads, maybe some non-detonated bombs ? That could randomly explode.
There should also be a specific ambiance to each place, maybe some musical ambiance, a musical / apocalyptic ambiance in cities .