Personally, I'm a long way from convinced this would work. A player approaches an open world with ambition and a keenness to explore, not with the kind of apprehension and dread that one would associate with horror. Horror is told very much through the environment and that environment is meant to make you feel trapped and desperate. An open world is all about empowerment and opportunity. It's meant to make the player feel important and powerful, not what one want's to feel in horror game.
To me, this more likely to work if Capcom focused less on the horror in this open world Resident Evil game and for the game to be like the more action orientated games in the series, like 4. The obvious problem with that is that at least a significant portion of the fanbase would be put off by that after seen some great horror games and remasters from the series in recent years. A Resident Evil open world has another more indigenous problem. Unlike other companies like Ubisoft or Bethesda, Capcom isn't exactly known for it's open worlds. When they have given it a go, it's been to mixed success. Sorry, but I do see Capcom making a mess of it, especially if they do try to squeeze the square block that is survival-horror into the round hole of an open world.