^History Phd student from the UK. Most Arab tribes did convert to Islam after the Hijra and in the years after the prophet's death. Due to the lack of sources, we cannot be sure how many, but by the time of the Caliph Abd al-Malik ibn Marwan (685-705 AD.) it is clear that most people who spoke Arabic would have followed an early form of Islam, or would have been ruled by those following Islam, converting later.

Some Arab tribespeople did continue to follow non-Islamic religions well into the late Umayyad period (ending in 750 AD). In particular, the Sabeans of an area known as Al Jazira, now part of Syria, followed a pre-Christian pagan religion, but were still Arabs. Until recently, (they were wiped out by Daesh last year) people still claimed to be Sabean. They survived due to their identification with a religious group mentioned in the Koran. The other surviving religious groups amongst the Arabs all survived for particular local reasons. In Yemen, for example, Christian influence from Ethiopia was strong and there is some scattered evidence to suggest a move of Arab speakers from Yemen to Ethiopia during the early Caliphate. However, unfortunately, we can never know too much of this for sure. The early Muslims were not in the habit of writing things down, and many would argue that even the Koran, is written long after the events I've just described.