It's still available for the Model X and Model S. The disclosure when you pay for it is very clear. They are not acting sketchy when they sell it to you. I'd guess it has more to do with not enough people ordering it, so removing the option streamlines fulfillment.
> I suspect they're finding the shipped hardware isn't enough to accomplish what they want with the necessary reliability.
Yeah they already admitted to this. Anyone who has paid for full self driving is getting a Hardware 3.0 (HW3) upgrade for free. They said full self driving will require HW3.
> Total speculation, but I'd bet a chocolate chip cookie that they'll find they need to make changes to the sensor array as well.
Yeah, as an owner I'm pretty worried that will be the case but I guess we will see. I doubt they will admit to this publicly though - they seem adamant that the sensors today should be sufficient.