Technically, they didn't. They said the ac7260 itself would be available for Q2. They never actually claimed anything about 7 drivers being ready anymore precisely than "soon".
Now that I'm done playing devil's advocate, I will say that this is a joke. Ignore, for the moment, that I utterly despise Windows and everything MS stands for and refuse to use any of their products. Manufacturers announcing a product will be ready, by a certain point, implies that the product will have drivers to go along with it. The fact that Intel has left over 50% of Windows users in the lurch with this is completely unacceptable. That they're marketing the ac7260 as OEM is even worse. Not only is Intel essentially telling the consumer to get bent, they're also telling manufacturers the same thing. Not even ASUS (my favorite hardware company), who are notorious for releasing products with buggy, half baked, and occasionally useless firmware and drivers, ever pulled a stunt like this, as far as I know. No driver at all. Totally absurd!