I like the Sri Lanka idea or Southeast Asia. I would like to see a flesh out jungle environment instead of the small one we had in Sun and Moon.
Also every landscape except for a sandy desert can be covered.
UK: I like the idea of London being a large metropolitan city and I believe it would be cool to explore large plains or even medieval castles sounds pretty intriguing in my opinion.
Australia: We could see many weird looking Pokemon there and some vast deserts as well.
Germany: Kinda surprised they haven't made one already given how much influence this country has to the Japanese. I guess we could see very unique cities there.
Italy: I think a city like Milano or Rome would be a waste to not appear in Pokemon imo.
Greece:My bias might play a part here but well given our vast mythology and the fact that we have many islands and mountain areas this could potentially make a quite exciting journey. I would also love to see Olympic Games for Pokemon as well.
Well, it does at least stretch into the Arctic. And if there were going to be new megas in this region, I would have hopes for Mega Beartic (with Water as secondary typing) happening. ^^Back during the pre-release of Sun & Moon, there's been speculation and discussion around the Canada-France-Hawaii Telescope.
I know this doesn't mean anything. But I don't have any problem if it ends up being Canada.