This has been asked plenty of times before already, but it's a fun question.
Islam will not come into existence - aside from the huge number of butterflies that will prevent Muhammad being born anyway, Islam was heavily influenced by Christianity.
What would we see? Well, a much less monotheistic world, and no Abrahamic influence of mankind - it will be reduced to what it was before Christianity, a small faith centered in the Levant, and nothing else.
Here's a possible map of what we could see as the major religions of the middle east in the year 500 AD:
Neon blue = Tengriist (assuming turks still migrate west)
Crimson = Iberian Paganism
Dark green = Arab Paganism
Teal blue = Zoroastrianism
Orange = Hinduism
Yellow = Buddhist
Pink = Judaism
Dark red = Hellenic Paganism
Dark blue = Egyptian Paganism
Light green = African beliefs
What would happen beyond that is hard to tell. This map of course is assuming no other major religions pop up in Christianity's place.