The plain and simple answer is no. There is no guarantee that all of the seeds you purchase will germinate. Sometimes the grower's fault, and sometimes it's the seller's responsibility. However, the failure rate is often quite low, especially when seed banks purchase seeds. The failure rate can be as low as 10% to 20%, which indicates that most of your seeds (or possibly all) will mature into plants. However, you should always be prepared for the unusual potential of some of them not germinating.