Only if the industry as a whole agrees to not cut rates, and nobody new enters the market. In a competitive market, if the cost goes down (as would happen with fewer accidents) then the rates will drop.

I'm curious if we could see a future where the car manufacturers provide insurance for their product, and you would buy a combined hardware/software/updates/insurance subscription package from a manufacturer. It seems like the inevitable conclusion of all the debate around who's ultimately responsible for the actions a self-driving car takes.