Insurance won't insure for what they don't understand and build a risk model for. I can assure they won't understand something like this for a very long time.
I'm not sure they need to understand bitcoin specifically to build a risk model, wouldn't they just need general data on losses suffered by various internet hosts due to hacking attacks? Doesn't really matter exactly what is stolen as long as they have a corpus of data on the value of everything that is stolen in this manner. Bitcoin wallets probably fit somewhere in the payoff curve for that.