A lot of what ifs there man.
And I'll go out on a limb and say it can't happen. Simply because it's support would be minimal, because it didn't come with the console.
I hate to sound like a broken record here, but never in this industry have we seen a peripheral become the standard if it wasn't the standard to begin with. Developers fully support what's in the console.
It's why so many 360 games don't rely on the HDD, it's why the EyeToy got so little of support, so few PS2 titles even had the HDD as an option, so few games used the RAM expansion of the N64, and so few games used the analog sticks on the Dual Shock.
If it's not there in the beginning, there's no guarantee that enough people will buy it, and if your game is made for it, there's no guarantee it will be bought, because of those limitations.
It won't happen as long as motion sensing controllers like this aren't packed in with the 360, PS3, or PS2. And even if they are one day, for the 360 and PS2 it would be too late. Too many units without said controller.
If Sony dropped all PS3's with the Sixaxis today, and started selling them with Wiimote knock offs it might be soon enough to actually become the standard. For the others the 360 and specifically the PS2 it's way too late.