There's a pretty distinct difference between the vision the CBC and BBC have for a streaming-dominant future and the US TV system.
The CBC operates its entire transmission system itself, and the BBC controls its entire transmission system (though the actual transmitter sites are now operated by private contractors.)
The BBC has a mandate to provide service to essentially everyone in the UK, since everyone (pretty much) pays the annual TV license fee. The CBC attempted to do the same in the analog era, but didn't have the funding to convert the entirety of its network to digital when the time came.
The US system, of course, is far more convoluted and less centralized. Local TV was lucrative enough as a business that even without any national service mandate, individual broadcasters took only about 15 years (let's say 1948 to 1963) to build out enough local stations to provide something like 98% population coverage and better than 90% land coverage.
Nearly all of those stations were still profitable enough in the late 00s that they were able to convert to ATSC 1 DTV and continue providing OTA service to well north of 95% of US pop count. (Apologies to Albin, Wyoming.)
BUT: the business model for US broadcast TV has changed dramatically in the 15 years since analog shutdown, of course. Local stations that made most of their money from network retransmission payments (money coming FROM the network TO the local stations) and from selling local ads to local businesses had to change course - now the biggest source of income to local stations is the retrans consent money they get from cable and satellite companies, while local stations pay fees TO the networks for the programming they carry.
Local news can still be something of a profit center, but the audience is shrinking and aging rapidly.
The big group operators (Nexstar, Sinclair, Gray, Scripps, etc) that own the bulk of those local stations have already done some of the things Kirk reinvented: master control operations are largely centralized at a handful of hubs around the country, and some aspects of newscasts are also centralized, whether it's statewide weather operations or national graphics production or what have you.
So why aren't all these stations going to go away any time soon? Because it's still basically a decentralized system that can't be easily unraveled to create a more nationalized one. Cable and satellite retrans dollars only go to actual broadcast stations, so the transmitters have to stay on the air in some form in each DMA or else Gray, Nexstar, Sinclair et al. (and NBC/ABC/CBS/Fox for their O&Os) can't tap into retrans revenue. Most of the expense of broadcast TV transmission is a sunk cost at this point - a LOT of towers were rebuilt or reinforced for DTV just 15 years ago and are good to go for a couple more decades. We're down to just 138 MHz of UHF spectrum being used for TV (470-608 MHz, or channels 14-36), and that part of the spectrum is less desirable for mobile use at this point, since the wavelengths are getting too long to use in mobile devices, so there's less money to be had from selling off remaining TV spectrum.
Here's what I think WILL happen over the next decade or so:
There's something of a crisis coming with cable retrans money for broadcast TV, because the number of cable subscribers paying $20+ a month in "broadcast fees" is cratering. So there's less revenue heading for local TV in coming years. That's going to reduce local TV station budgets, of course.
Regionalizing "local" TV news doesn't really work. Spectrum has been trying that, and the results have been 24-hour channels providing nothing useful to anyone. Here in upstate New York, nobody in Syracuse cares about news from Rochester and Rochester doesn't care about Syracuse, never mind Buffalo or Albany or Yonkers. Start doing that to broadcast news stations and you'll watch ratings plummet, especially if the competition is still more local. Some broadcasters will continue the trend Sinclair has started of pulling the plug entirely on local news in unprofitable areas, but that's risky, too - you run the risk of losing the unique local content that keeps drawing remaining linear viewers.
In markets with little to no OTA viewership (Palm Springs, Fort Myers, Binghamton), it's easy to imagine stations being willing to shut down ATSC 1.0 signals in the next few years and consolidate all their 3.0 signals on a single transmitter that will be cheaper to run. Markets with more 1.0 viewership might also see some consolidation of those 1.0 signals on "lighthouse" transmitters. There's no reason to downgrade video resolution or audio to do any of that, though - improvements in encoding take care of that nicely for video, and audio consumes only a tiny portion of the total DTV bitrate.
Beyond that? Before anything happens technologically, we're looking at regulatory and business changes. Will the current model of network affiliation last another 15 years? That, to me, is a much more interesting area of speculation than some future 480i multiplex or whatever.
