You can setup your pre-order to turn off automatically when quantity limits are reached or when the pre-order schedule date is expired. To do so, please go to Products page and go to the product you wish to configure and click on Default/Custom Settings:
At If Pre-order is closed due to limit or date, select Automatically set Pre-order to OFF option:
Each time Pre-Order quantity limit is reached or schedule date expires, the Pre-Order will automatically turn off:
You can only set this on an individual product level only. Future releases will enable you to set this as a default setting.