The room will become available to book again, but not necessarily at a discounted rate. If the discount is still a current offer, then yes, it’s possible, but no one can really say for sure. If the discount has already expired, then no.
I find that if the offer is relatively new, there is a decent chance of picking up the room you want as inventory changes a lot as people cancel and rebook. But if the offer has been around for awhile, or set to expire soon, I’m not so certain those rooms get put back in the discounted pot.