Look at the following verses:
20: And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation.
16: These are the sons of Ishmael, and these are their names, by their towns, and by their castles; twelve princes according to their nations. 17: And these are the years of the life of Ishmael, an hundred and thirty and seven years: and he gave up the ghost and died; and was gathered unto his people. 18: And they dwelt from Havilah unto Shur, that is before Egypt, as thou goest toward Assyria: and he died in the presence of all his brethren.
There is more to this story. I would suggest reading all of Genesis. It tells me that God did promise His blessing on the decendents of Ishmael...