I hope they go with a Pax Romana type of map, that covers the UK, Western Europe, and Northern Africa. The continent has a lot of cool features that would nice to see fit into the game. They could bring back the rail system for you to commute between England and France. The Netherlands can be a big boating industrial area. My guess is if there is a Gym there it would be either Water or Grass. And you even get to bring back some snow covered territories with the Scandinavian countries.
My hope would be that Northern Africa opens up post the Elite Four. I hope that area, or whatever area we get, is as big if not bigger than the post-E4 Unova in BW2. Egypt would be fun, though we already have Cofagrigus and Krookodile. I guess maybe a Psychic cat might be a good addition.
It will be interesting to see how Italy and Greece get played. They could bring back a Church focused city for the Vatican and they could delve deeper into the history of Pokemon with Greece.
Another thing I'm really hoping for is that the side game (Contest, Pokelethon, Musical) is the Olympics. I know it would be a lot like the Pokelethon, but they could do more games, possibly model some after actual Olympic sports.
I wonder if they will include Fantina.