Since you no longer have possession of the vehicle then technically you could cancel your policy. It's important to keep in mind, though, that if you have been continuously insured for 6 months or more you will lose a discount if your policy cancels. If you were not planning on getting another vehicle for an extended period of time then it would make sense to cancel your policy since you would be paying for months of coverage for no reason. However, if you are planning on getting a different vehicle in less than a month, your rate will be more expensive
if you cancel rather than maintain your active policy. I would recommend paying your bill and updating the vehicle on your policy once you get a new one for the best savings on your car insurance.