I'm hoping either Australia or the United Kingdom. Game Freak seem to always choose well known locations for where regions are based from, whether it be single states or whole countries. Australia would most likely have a similar climate to Alola, except a larger desert, more cities, bushes, caves and swamps, which would be perfect for a Pokémon game. Another reason why Australia would be good, is all the lore we have, the Old Melbourne Gaol (the Aussie way of spelling "jail") could be a hive for Ghost-Type Pokémon and a ghost storyline (A la Old Chateau, Strange House, Hex Maniac and Abandoned Thrifty Megamart), maybe they could split Sydney in two (due to the Sydney Harbour Bridge).