They have been in Sri Lanka for a while where there are even locally developed varieties.It is not much of a stretch for them to move onto Southern India.
Unfortunately that's not correct. For some reason it's a huge stretch. Sri Lanka has also been growing mangosteen and durian for quite a long time, but they also have yet to make it to India. India seems very resistant to adopting new fruits.
One fruit that is just now starting to make some headway in India is kiwi. I saw some in N. India and was surprised. They were locally grown and quite small.