Western Asia (including the Indian Subcontinent):
Probability: Near Definite
Middle East
Probability: Likely
Though the region was hit nearly as hard as North Africa was during the Arab Spring, many countries were able to dodge the political and civil turmoil of that Season. Countries like Bahrain, Qatar, and U.A.E. suffered little to no problems. More countries still have since become stable and safe again (Jordan and Oman), and could easily constitute visits as well. The Caucus States (Georgia, Armenia, Azerbaijan) probably will not receive a visit for the next few seasons, and the same for Turkey. Israel, I will say time and again is more feasible than people let on. Now with the Arab Spring in the past, and at very least one other Race franchise racing there with little to no problems, its all the more likely that this will be a location soon (prob not this year tho)
Central Asia
Probability: Possible
This is one region that I believe will receive a surprise visit in the very near future (similar to Azerbaijan in S20). Whether it's a return to Kazakhstan, or a visit to Uzbekistan, it will be a great look at region that too often gets overlooked.
South Asia
Probability: Highly Likely
India is one of the race's "Old Faithfuls." Time and again they take contestants there, and it still produces some of the most profound, emotional, and exciting legs of each of the seasons that it's featured. Although I know that there are many different cultures within India, let alone each of the surrounding nations within the region, the average American viewer most likely does not- so, places like Bangladesh (not likely due to visit in S21), and Sri Lanka are nearly completely interchangeable with India. One of the three is bound to be featured this season. Nepal and Maldives could also host a leg or two each, as well. Those two may be featured sooner than we all think.