The risk may decrease but liability may increase, as this is a risk you are taking deliberately if you decide to drive your car instead of getting a safe self driving car like everybody else.
Insurance doesn't work that way. Liability isn't an ephemeral concept, it's the chance of a claim X the amount of a claim, pooled in a group of buyers with differing risks. The relative cost of insurance compared to an autonomous vehicle should increase, but not the dollar amount.
