Those same arguments were used against the creation of the Met Council and the MUSA line in the first place. That it hasn't happened has something to do with the fact that most people don't move to a place solely based on the cost of housing.even if we were to stop building greenfield developments in the metro, it might just result in people choosing to live somewhere else rather than moving into the city. I don't think it's a foregone conclusion that density and the urban population will increase as a result.
Although it has more to do with the fact that stopping exurban greenfield tract housing development does not end new housing development. On top of teardown activity, there are plenty of parcels available for smaller-scale development.
We've had 70 years to tally up all the ways that Levittown-type developments were a net negative to the public treasury, to the degree that we've forgotten about the shoddy building techniques that most developers used in those days to keep prices low (a big part of the reason new houses have higher sticker prices is that building codes have increased, allowing buyers to save the tens of thousands they would have to spend in the 50s to make up for the corners cut by developers).