Silvers are at the bottom of the list when it comes to upgrades. And discounted economy will put you lower than other silvers with a higher fare class.
The variables are things like how big is the F cabin, how much paid F is there on the route and what is the pattern of elite travel on the route (and day in question). You might ask over in the DL forum as people there probably have a better feel of those things.
That being said, while your chances aren't "nil" they are likely pretty small. Don't expect the upgrade and be happy if it comes.