No doubt Steve is irreplaceable, but Apple is going to be building his products for at least the next 2 years. He left a 5-year product plan. Nothing like knowing you're going to die for a year or more -- working with the same fierce focus he always had -- to map your legacy.
Apple isn't 'over.' Not just the fanboys, but some smart money says so:
Carl Icahn, Who Can't Stop Buying Apple, Just Bought $500 Million More - Forbes