Not necessarily. Our fares can change for many reasons, including how many seats we have on that flight (the supply), how many people have bought tickets on that flight (the demand), and other factors. We also closely monitor pricing on flights and adjust our fares to stay competitive. As a result, fares can change at any time, even while you are shopping.
If you find a lower fare later, you can always change your reservation or add a Wanna Get Away Plus ticket and receive the difference as a flight credit. Or, if you purchased a ticket that includes refundability, you will have the option to refund the difference back to your original form of payment.