There are repercussions to the tenant if this were to happen, such as:
The tenants are required to pay one weeks rent as a penalty fee.
Rent until a new tenant takes over or the fixed term period ends, whichever occurs first, and
A percentage of the advertising costs and the agent’s reletting fee. For example, if a tenant breaks the lease 9 months into a 12-month tenancy there is 25% of the lease remaining, so they would be expected to pay 25% of these amounts.
If your property manager is pro active and works with the tenants this should not affect rental payments to you as the landlord as once new tenants are found their agreement should start the day after the old tenancy agreement is terminated. This applies for NSW and QLD.