I am guessing since they only visited India and Japan for Season 20 and they are bound to touch Asia (More like South-east Asia or Asian countries) for every season...
20: India and Japan
19: Taiwan, Indonesia, Thailand
18: Japan, China, India
17: Bangladesh, Hong Kong, South Korea
16: Malaysia, Singapore, China
15: Japan, Vietnam, Cambodia
14: India, Thailand, China
From what we can see, they try to visit China (or part of China like Hong Kong or Taiwan every season... and TAR 20 is an exception with no Chinese countries at all as well as TAR 15)
I predict at least 2 legs in China (with one of it being NEL -_-), no more Japan and India. No India, but not ruling out places like Sri Lanka or Bangladesh again.
TAR also really like Malaysia and there's many places not visited in Malaysia as well. So if they're visiting Malaysia, they might make a trip down to Singapore again like TAR 3 and TAR 16.
I have a feeling they will be visiting at least 1 middle east country in Asia such as Kuwait, Turkey, Oman, Kazakhstan and Israel. They might visit Israel if they want to clog up new countries which they can use in their previews.
I also think, Philippines is due for a visit too.
Asian countries I would really like to see would be Philippines and Laos or Brunei.
But gut feeling tells me China will definitely be visited and the other 2 asian countries will most probably be Cambodia/Vietnam and Sri Lanka/Bangladesh.