The odds you get sued from walking away from an auto-renewal are low. The claims, even if valid, are almost certainly not worth the legal fees and expenses.
The odds you get sent to a collections agency, or at least a collections department, and are threatened in some fashion? High.
But don’t do it. If you haven’t earned the renewal, you haven’t earned it. If you threaten a customer, there is a small chance they’ll still pay. But you’ll turn them into someone who would Never Recommend to a Friend for life. Just for a few nickels that will never recur anyway.
Don’t waste time chasing non-recurring customers and revenue. Focus on the ones that will be with you the rest of the journey.