How sure are they that this hardware revision is going to be what is required? I feel like at any point in time you can make an assumption about the hardware requirements to only discover in future that you could have actually done it with just a software update if the CPU had one more core. They'd have to be pretty sure this HW rev would meet their future demands for self-driving right ?
That, and judging by Tesla's history - if there was indeed something lacking, they might just retro-fit it for free onto people's cars. So I assume they're keen on getting this right...haha.