Could this force universities to finally decrease costs?
Probably wishful thinking, the most desirable programs will just pivot to recruiting international students
Nope. They are expensive programs because you have to compensate all of these highly skilled professors that are dentists, pharmacists, doctors, lawyers, clinical psychologists, etc for the opportunity cost of their time. If you tell somebody who is normally earning $300,000 that their new teaching pay is going to be $150,000, you won't be able to run a training program at all.
And this ignores all of the complex training equipment, pharmaceuticals, reagents, , specialized facilities, etc which have already been purchased , oftentimes from loans by educational institutions at predefined, long-term interest rates.
So this will act exactly like a tariffs do. Just like the importer can't magically reduce the price of the item because a tariffs made it expensive, The schools can't reduce the cost of their professional programs.
I suspect that more programs will open their doors to foreigners. For every under represented medical or legal applicant , there are thousands of wealthy foreigners who would love to get those coveted American slots. Up until now the foreign slots have been restricted. But that may change