It would be nice, but I don't think it will happen.
You could use a macro with a flag condition, and turn the flag off or on to change the behavior.
I'd suggest replacing the batteries with a low-voltage power supply, but butting power resets the settings on the unit.
Another option might be to use a PowerFlash with non-x10 wired motion sensor. You could either have conditional macros (like the above solution), or you could plug the PowerFlash into an Appliance Module, and just turn it off when you want to deactivate the motion sensor.