The biggest issue that I have with Autopilot Device Preparation is that the hardware isn't tied to our tenant by uploading a hash.

There is nothing to prevent a use setting up a device with a personal account, e.g. they have left the business & not returned the equipment or setting it up with another tenant.

Traditional Autopilot locks the device to our tenant as long as it can access the appropriate Microsoft endpoints. 

Device Association sounds like it may resolve that, any vague ideas on timeline?