There has been no official Press Release of this matter. The only thing that has been stated is that SP3 wont be out until AFTER Vista gets released. Since Vista is now pushed back till Janurary then SP3 wont be till later than that.
The SP3 you friend might have gotten could have been from The HotFix
which isnt real and is also full of spyware. As for the Beta of SP3 from M$ i have not heard that they even released it yet.