The new law simply removes the requirement for airports to manage their own internal transportation. So it leaves the possibility for public transit to connect

The new law simply removes the requirement for airports to manage their own internal transportation. So it leaves the possibility for public transit to connect riders directly to terminals, which was previously not allowed. This doesn't force airports to use Public Transportation or restrict them from doing what they are already doing. The fact that most large airports where this would apply are already built to use the system the way it is, seems to me that it is unlikely we will see any change for at least a few decades. This change is a significant overhaul of the organization and layout of an airport. Airports aren't changing that often and new ones don't pop up very often. Likewise, I am not sure the demand for the change is really there to pressure airports to change. From the airport user's perspective, the only change is that they could now take public transportation directly to the terminal that their plane is at. This is different than the current system where you get off of public transportation at a main terminal, check your bags, get tickets, go through security, etc and then board an automated train to go to an auxiliary terminal where the plane is located.