I know profit motivated attacks have eclipsed entertainment motivated ones, but that's partly been about the work required to get a 'strong' exploit going. Mirai used an easier access vector than Morris to get full ownership of target devices, so it wouldn't be hard for one person to copy and abuse.

I don't think this is going to become the norm - messing up a refrigerator isn't a lucrative goal - but I expect that it'll happen occasionally if systems stay this weak.