This would likely depend on the terms of your agreement, It the agreement specified a specific property, purchasing party, and other terms specific to an agreement a non-sale may void the agreement. On the other hand, if the verbiage is open ended stating that the agreement is based on only the sale of your property, you may be committed to a longer term.
Generally, sellers don't want to waste their time waiting on a property that and/or an agreement that stands little chance of reaching a successful closing.
Your real estate professional should be able to guide you through this. Their knowledge of the purchase agreement should prove invaluable.