Yes, the more time passes, the more missile batteries are built and deployed to the south.
And that is just with the older Nasr and Noor models—radar-guided missiles that are consequently vulnerable to being blinded or destroyed once their emissions are detected.
However, if the United States persists, Iran could develop newer, more precise systems—such as equipping the Noor missile with an infrared seeker or utilizing alternatives like the Fath-360.
The latter’s range and trajectory allow for easy launching from behind mountain cover, if they are equipped with a guidance system capable of tracking moving targets—a capability that shouldn't be difficult to achieve, judging by the advancements seen in larger ballistic missiles.