Honestly GTA V and Fallout 4 are perfect examples of what you are asking for, just not what you want. Open world games can't by design have the ability to be as varied as linear, level based games. So what we have is sectional variation. The city, the desert, the slums, the beach, the residential, the forest - gta 5 is INSANELY varied. Fallout 4 also has this...forest/woods, cities, highways, the glowing sea, small encampments and faux settlements/towns.

Open-world games should not take the easy road of plunking down an open world and dusting off their hands. They need to take some bits from linear games and find clever ways to introduce new locations, even if that means changing maps or whatever else.

This is inherently the problem with unlocking the entire map all at once. Fallout 4 and GTA 5 want you to follow the story and see what is out there, just like fallout 3, but the developers know a large chunk of players are just going to go exploring so they don't hold anything back. Personally I don't want this to change because it ruins the design of an open world game and what they are meant to be. Can you imagine the backlash if the strip on new vegas was locked behind a story mission? Or that vaults were locked to side quests? What about the top half of the map on gta 5 being locked to Trevor only? GTA 3 only did it due to limitations with hardware and technology, but with cheats you could easily go from one map to the next via car jumps/flying car, and it was hilarious. I've been pretty impressed with how fallout 4 and gta 5 have their worlds designed and would rather see more variation within the map for future games than locked sections.