With a game this massive, it wouldn't be unheard of for the map to be so expansively large that most people, even at the highest levels, haven't seen all of there is to see. It would also have a massive player base. Maybe even based out of a small number of servers, to ensure that everything is populated? And for such a large game, I think there would have to be a quest generator and NPCs that had real personalities and could respond to actual speech in order to make that plausible. It's technology that's currently in the works and many of its researchers are finding it to be very possible. But that's not really that important, seeing as this is fiction and we can do whatever we want. XD Therefore, quests which appear on the borders between Sci-Fi and Fantasy would likely almost require people from either side. I also think it wouldn't be too crazy to think there are even some cities/settlements on either side of the map that draw in both elements. Meaning some cities in the Fantasy zone have a high-tech style to them which is woven in with the natural and magical themes of Fantasy. On the other side, it would be the cyberpunk cities that promote agricultural/harmony with nature and technologically augmented magic (or vise-versa, magically augmented tech).
The risk areas would work fine, I think. I'm sure that mods and whatnot would still do patrols, but to a degree the "safety" would have to be programmed in for players to be protected from PK in low-level zones or from PK'ers of a crazy high level difference. Players could privately exchange e-mails/contact info if they liked, so that they could talk about the game outside the game, or kind of just chat when they didn't want to play their characters, etc.