I think we'll be seeing LA's subway development as a model for the future of infrastructure.
The big problem with urban highways is that if you build the highway first and do not include higher-density transit, the neighborhood develops in a suburb-esque highway fashion, as distance of the house/apartment from the highway exit doesn't make a huge difference in commute time, whereas a train commute requires you to walk that last leg.
The issue I imagine many planners are facing is "how do we build useful, medium to high density public transit that actually serves a decent amount of people?" And it's a hard problem, because the neighborhood layouts are designed for highways. New transit projects other than highways face opposition because they don't appear useful to most of the residents.
I went to LA recently and rode the subway a bunch, into Downtown LA and back out to my friend's more suburban apartment near Universal City. Once, I took an Uber and the driver pointed out to me all of the new higher-density residential development taking place around the edges of the urban core (and noted it improved the safety of the area dramatically, "people are walking around now! no more gangs!").
Basically, the neighborhood was reshaping toward a more transit-friendly environment after some useful public transit was implemented.
The current problem is convincing cities to fund transit lines when they seem to "go to nowhere useful". If LA continues to be successful at building subways, they'll provide a great piece of evidence and support for building new higher-density transit in other cities throughout the country.