Q. If I activate my reference machine then use Sysprep on it and clone it, will I still need to activate the machines where I restore the image?

A. Yes, you'll need to reactivate. Running Sysprep performs a rearm, which resets the grace period until activation is required and marks the image as un-activated. Even if you didn't run Sysprep, if the hardware an OS is running on changes significantly, the machines have to be reactivated anyway. This would certainly be the case if you take an OS and put it in another physical box, even if the components are identical.