I agree that India seems to be the next major destination, and that somewhere in the south Pacific is probably another site, perhaps after India. I also believe that the dogsled site is probably Alaska or Yukon. However, I believe there is another possibility for Frank's ice water swim.New Zealand has some high mountains (up to 12,349 feet) and it is in the Southern Hemisphere. This means it would be winter there when it is summer in the Northern Hemisphere. The scenes in Europe were obviously chilly, but certainly not filmed in the dead of winter.
Therefore, it is possible to set up for a frigidly cold swim "down under" followed by a flight to "the land of the midnight sun" for a frigidly cold dogsled run. It would be a pretty cool (pardon the pun!) thing to do gimmick-wise. It also lets them clearly include Down Under in the previews without totally giving it away like it would if they showed a koala or a kangaroo.
Another reason for a Down Under site...so far they have visited North America, Africa, Europe, and are obviously going to Asia. Assuming no easy way to Antarctica, then we have to include Down Under and South America in order to hit all the continents except Antarctica.
Based on this, here are five possible major routes:
(1) India, South Pacific, New Zealand/Australia, Alaska/Yukon, South America (best gimmick route...hot-hot-cold-cold-hot)
(2) India, New Zealand/Australia, Alaska/Yukon, South Pacific, South America (gimmick variation...hot-cold-cold-hot-hot)
(3) India, New Zealand/Australia, South Pacific, South America, Alaska/Yukon (zig-zag a la Europe/Africa)
(4) India, South Pacific, New Zealand/Australia, South America, Alaska/Yukon (most efficient travel-wise)
(5) India, New Zealand/Australia, South America, South Pacific, Alaska/Yukon (most travel weary)
OK...my brain is tired now. Some of you other spoilers chew this up, massage it a bit, and see if it has any merit. I eagerly await your input!