I'm sure it's possible. People get addicted to alcohol, drugs, gambling, lying, and all sorts of other things, so why not sex toys?
Sex toys are meant for enhancing one's sex life, not replacing a real person. Once you learn how to get off with a sex toy, it can be quick and direct. You get off. With a person, there's directing, asking, pushing, telling, and still you're not guaranteed an orgasm. However, with a real person, you have emotions, feelings, and hopefully love.