Feedback modal upon exiting beta

We're releasing a new feature which will be beta tested. We're exploring ways in which we can collect feedback about the feature and one way was to surface a modal if the user decides to opt-out of the beta. At this point, we would display a modal, with 2 questions, both optional.

If the user clicks "Submit feedback" the form data will be submitted and the user would be taken to the 'old' service. If the user clicks "Cancel" the modal will close and they will remain in the beta.

My question is, is it acceptable to surface a feedback modal at this point?, and should I include a third button which would allow the user to exit the beta without giving feedback?