Its a cultural thing. People get what they want when they want it.
Thats why you have to have strong policies to prevent this from happening. This exact thing can happen with any computer manufacturer and is completely irrelevant to the date. Apple can tell you the date and time of the OS release and it doesnt matter if you cant certify it before hand - something you can do with the DPs and the GM.
If people will upgrade their computer on Day 1, they can do that for another OS and they will do it outside of certification, hang a date of release is going to mean little to them. The only way you can do this is to set a firm policy and say that anybody who violates it wont get supported until they are on a supported platform. I dont give jack about entitlement. If you work in business you need a firm IT policy that you can back up with management. YOu have to control your employees and their equipment or you will never be able to properly support them.
Look at it this way. Anybody can upgrade to the newest OS on day one on any platform. In any industry. Without knowing the specific date. Without the approval of the IT department. Even with technical polices in place. Of course most employees dont do that because they know that they wont get supported by their department. You have to be firm with people and let them know you are serious. If they dont respect polices in place that is a problem that no tech company can and should address. Any time you have even a vague date you should be working to make sure you can support it.