These days it's more likely that new freeways will extend outward from beltways in a manner calculated to minimize property acquisition cost. No agency -- or roadway backing entity -- wants to incur the cost, both fiscal and political, of plowing a freeway through either dense urban or even moderately dense suburban territory. The era of central-city freeway building (at least in respect to new facilities) is past.
That may be the current philosophy (with 2 noted exceptions along I-49 for Shreveport and Lafayette). But let's see how that philosophy holds up over the next 10-20 years. The United States has a bunch of urban zones whose high priced economics make them mathematically unsustainable over the long term. They're bubbles waiting to burst (the situation isn't much better for all those clusters of McMansions in the suburbs and exhurbs either). Right now it's politically, financially and logistically impossible to plow a new freeway to or thru a city center experiencing a trendy renaissance. How difficult will it be 20 years from now when the same zone may be struggling to attract new residents, businesses and customers?
Young adults are getting better and better at avoiding having kids and the soaring costs of parenthood. For people born in the United States we're now getting into negative territory: more people dying than being born. Combine that with the current anti-immigrant fervor, extreme costs of health care, child care, housing, etc and it creates the potential for a serious down-turn in population growth. Add age demographic imbalance to the equation. Our population will be top-heavy with retirement age citizens and short on young, working age adults. All of that added together could create quite the downturn in those pricey city centers.
Ever-improving technology is making it less necessary to work or live in a high priced city, much less a very high priced city center. The same thing goes for even traveling to that city center. Brick and mortar retail is taking a beating from online merchants. Pro sports events and concerts are often price-gouging rip-offs. You can often get a better experience watching the event on the giant 4K UHDTV in the living room. They're building bike paths and other types of green space in these urban centers. There will be fewer people who can afford to live near those attractions. Screw driving a long distance in stop-&-go traffic or taking forever on a bus or train to get there either.
Of course if a downtown/urban center falls into a serious down-turn no one is going to be very enthused about building a new freeway through that zone unless there's an obvious benefit to doing so.