There are still Arabs living in Central Asia, mainly in Bukhara and Samarkand areas in Uzbekistan and a smaller group in Tajikistan.
They try to keep their identity and Arab girls usually do not marry Uzbeks and Tajiks. Most of thems speak Uzbek and Tajik also some were able to keep Arab language.
I don't no much about how many of them live in Central Asia now. According to Soviet sources there were about 3 thousands Central Asian Arabs in 1989.
I know that some Arabs tribes also live in Afghanistan.
Among Kazakhs there is a clan called "Kozha" which originated from Arabs, who taught muslims to Kazakhs. Some of these Arabs even were Muhammed's descendants.