Hello,
The "pre-order" plugin just perform overrides on the HikaShop product quantity ; allowing you to have a "stock quantity" and a "pre order" quantity. When the "stock" is "0", then the sales are made on the "pre-order" value.
The plugin also allow you to override the "add to cart" button text when the stock is "0".
But if you want to add a notice regarding the availability delay, you will need to do it with an HikaShop custom field and it might require some custom code (PHP) in your HikaShop product page if you want to display only that field when the stock is "0".
Afterwards, if we have good specifications for a feature which can be used by every "pre-order" users ; it could be something which would add. I admit that right now I don't have a clear vision of it in a too specific a way and not enough flexible.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.