Per the email you get after "preparing for pre-order", yes, your credit card info is saved and ready to go at order time plus three days.
Per Apple email:
Changes and Availability
You can make changes to your iPhone selections and AppleCare+ coverage and remove any added accessories before you check out. Keep in mind that changes could affect your delivery estimate.
We’ll remember your preferred iPhone and payment method for three days after pre-order begins. Availability will be determined on a first-come, first-served basis at that time.