Thande, that's assuming Islam survives the defeat. After the Prophet Mohammed died, a lot of Muslim converts either went back to their traditional religions, or followed leaders who declared themselves to be the next prophets. These Muslim apostates were defeated in the Ridda wars right before the great Islamic invasions.
Since the invasions are defeated ITL, it is possible that the Caliphs are discredited, and that some Arab tribes revolt once again. Without the ability to reward followers in battle, Islam loses a lot of its appeal in this critical time in the religion's history. Some tribes could go back to their traditional religions, and new "prophets" establish themselves. Islam, if it survives, might be a small monotheistic sect, or a variety of similar sects. Such groups could retain their independence, or some might be eventually subsumed into Christianity and their beliefs seen as some strange heresy.
In any case, "Islam" ITL is likely to be very different than how it actually developed. It is not greatly exposed to Greek philosophy, lacks rich patrons, and might remain an oral tradition. If multiple sects exist, if the Quran is written down, there may be multiple versions based on the needs of its various prophets.