Speculation on TAR 31:
Well firstly in regards to possible locations, it may be safe to say that TAR is trying to create a trend of visiting countries that they have visited before one or two times and are due a new visit. From this trend, countries that fit this trend are:
North America: Canada, Costa Rica, Jamaica, Puerto Rico
South America: Bolivia, Ecuador, Uruguay, Paraguay
Europe: Croatia, Estonia, Finland, Hungary, Ireland (I think this is a very strong possibility), Lithuania, Romania, and Ukraine. Liechtenstein is a possibility too but very unlikely due to the size of the country and what they can do there.
Africa: South Africa, Egypt, Ethiopia, Ghana, Kenya, Mauritius, Mozambique, Senegal, Seychelles, Tunisia
Asia: Bangladesh, Cambodia, Oman, Taiwan, Azerbaijan, Kazakhstan, Kuwait, Mongolia
Oceania: Anything's fair game, although I think it's more likely to see Australia than New Zealand since it was visited in 18 whereas NZ was visited in 22.
Now for countries that are due a visit that have been visited frequently (last season visited is in parentheses):
South America: Chile (23)
Europe: Germany (26), Russia (21), United Kingdom (25), Austria (23), Spain (24), Sweden (25).
Asia: India (27), Japan (26), Malaysia (24)
I definitely think India and Japan are very strong contenders. It's been too long, and these are very frequent countries.
I also think there's a possibility of bringing back South Korea. When Indonesia was first introduced in 19, it came back 3 more times in the next 5 seasons, possibly because they realized how underused Indonesia was, and South Korea fits the underused, but highly accessible, category. We'll see though. I think the Philippines could fit this too, but not as well as South Korea does.
In terms of new visits, I think possible safe bets are Fiji, Laos, Nepal, Jordan, Coté d'Ivoire, Cameroon, Togo, then anything in Eastern Europe or the Caribbean is fair game. I would love to see one of the former-Soviet Central Asian states like Kyrgyzstan or Tajikstan, but due to accessibility, I find this unlikely.