Is there a way to know if a discount is going to be applied on a product? I have set up a number of discounts using Craft Commerce. Those discounts apply to specific groups of users and types of products. 

Is there a way to know inside the template, if a discount is going to be applied without checking the product type or user group of the current user?
Discounts can only be determined if the item is added to the cart. This is what separates a discount from a sale. 

A discount is actually not matched with the product but the line item as it sits on the order (with all of its context like the order's customer, etc)

You can determine if something is on sale with variant.onSale returning true or false.