Unreal Engine 4 has recently gone free to development on, with a 5% royalty fee after you ship and sell a game, which is awesome news for game creators, and gamers too since we’ll probably get more awesome games now.
With that news, UE4 is now capable of creating awesome open world levels by default, rather than having developers tweaking it a lot to achieve an open world game. They have a trailer for us to see (above) which looks great, but you can also see more of them, in a fixed shot, as animated gifs! More info on UE4 here.