It is a new region. Details have not been revealed yet, though the home place looks like it's based on Paris, France, or other parts of Europe because there's a tower that looks like the Eiffel Tower.
Here's some more stuff about this:
At the beginning of the trailer, Pikachu is standing on top of the Eifel Tower, and releasing a thunderbolt across the entire globe. This is significant because the game is taking place in a setting inspired by Europe, particularly France, and will experience a world wide release from this announcement at 11 am London time. - IGN thoroughly examining the details of the trailer.
Source: I watched the trailer.