First of all, Sony doesn't get to decide what the "defacto" controller is... the consumers do. Sony saying that is arrogance along the lines of - "we'll sell 5 million with no games."
Sony can push all they want, but the userbase wants DS3 instead, then DS3 it will be - eventually after the game sales tank and companies get the picture.
As for this, I say "bad move." If I want motion control, I have a Wii. Even on my Wii, I use the GC controller almost any time it is an option. I would wager that I am not the only one that feels this way.