Isn't the phrase in Hebrew, "ehye asher ehye" derived from an imperfect, and not present, form of the verb "hayah," so it should be rendered something more like "will be who I will be"? Also, the nominalized form of God's name that comes from this ("YHWH") is often connected with the phrase: "the God of your fathers, the God of Abraham, Isaac and Joseph." The self-identifying description seems to indicate two things, namely that it is this God, not any of the other purported gods, that is the source of being, the source of the world, now and forever, and that, just as YHWH was the God who established the covenant with the Patriarchs, he "will be" the God who keeps and fulfills the covenant in the future.
A better translation at any rate is 'I am that is', or so I've always thought.