No -- canceling a group is permanent.
Pay By Group never charges the cards of anyone in your group without your explicit permission, so there is no advantage to canceling a group over just letting it expire. The only thing canceling a group accomplishes is sending a very clear message that the group's goal is not going to happen. If there's even a chance that things will still come together, it's worth leaving the group open.
If you somehow canceled your group accidentally, Pay By Group support might be able to help you. Let them know what happened at firstname.lastname@example.org.