Geico recorded my purchase and said it would be covered at market value. No idea what would actually happen if the car were to be totaled. They didn't raise my rates or anything after I told them.
Total anecdote here, but one of my previous cars was a Lexus with the pre-collision system, about 14 years ago, during the earlier days of adaptive cruise tech. Unfortunately, the car was totaled, and when it came to insurance, it was a bit of a challenge determining the value. Basically, I didn't get much for it, because the demand wasn't there and calling around to local dealers showed a lack of inventory. So it was pretty much just a courtesy for my company to bump up the payout, because in the end, there wasn't much to objectively argue in my favor, that could demonstrably translate into increased value.
IMO, FSD will likely work similarly, if not worse. I mean, I can't imagine an insurance company could easily call a Tesla service center and figure out the take rate of FSD vehicles in the area. Meanwhile, insurance carriers already have "challenges" (I use this term loosely, and mainly through hearsay), determining the value of Tesla vehicles, which is part of the reason Tesla decided to start their own insurance company. It likely depends on the specific insurance company and office, but if my experience says anything, they're likely ignorant of the extent to which FSD even operates, much less how much it's worth- hell, Tesla owners (who likely know the system best), are in deep debate over its worth. I'm thinking insurance companies will likely find the closest equivalent to FSD, and depending on the customer relationship, either lowball on the value or do what happened to me, and just throw a bit of cash to keep the process moving.
I'd be curious to hear what Tesla insurance values the system at, but I don't think traditional providers will place much value on it. I'd find it even less likely that they'd treat it as an appreciating item, just because Elon raises the price.