Keep in mind, ATSC 1 signals are permitted to be shut down after five years of ATSC 3 broadcasts. I doubt that will happen that fast, but the day will come. MAYBE within the next ten years. But that day will come. Waste of valuable spectrum (& electricity & maintenance &…) to try and keep both going.
But if only so that the broadcasters can still point to "FREE" TV, but they would probably sell to wireless companies and cash out. Keep in mind that the vast majority of local stations today are owned by huge corporate interests who still can get revenue from cable and Sat for ATSC 1.0 while they will likely offer pay TV like HBO or ESPN behind a paywall at ATSC 3.0 (I see a viable, profitable niche business for Cable TV or Satellite once DTV and Dish merge) with streaming being a permanent alternative, but consumer fatigue of multiple billing and having to subscribe to too many streamers and their cost to meet the household needs/desires (expressed TODAY by many I speak with)--AND the very recent thoughts of unnamed sources at the studios about how they still make more money with cable/Sat revenue, and they should not turn out the lights there any time soon, especially since the big news of Netflix loss of subscribers. Nobody feel highly confident of where streaming is really going. I would say Disney+ and a few others are safe, and Netflix can fix their problem, so they should not be counted out, either, just yet.
The current rather LOW subscription rates for the newest studio streaming services are still NOT paying for all the new programming and tech on those services; it is revenue from both MVPD's and vMVPD's that are subsidizing the TRUE subscription cost, but with revenue decreasing from (v)MVPD's, the monthly subscription price will have to go up--AND it already has in almost every case, and at Disney+, as just one example.
It will take a little time, but consumer fatigue of ever increasing monthly subscription prices that are necessary to pay for all that NEW programming among several streaming services (several bills) will see a new "cut the cord" attitude, but by that time ATSC 1.0 is a diginets joke, and ATSC 3.0 will be behind a paywall, and vMVPD's may seem more appealing then they are even today, and that may be where the money REALLY is for the studios, with streaming seen as a secondary service for its vast catalog or a hybrid (v)MVPD subscription with a very modest add-on for full access to the streaming service for its catalog and opportunity to see missed episodes.
The real key would be the now AWFUL on one app, off that app, and load another experience needs to be fixed, and can be, but no so simply so. Accessing multiple streaming serviceslike the MVPD experience is what could make the difference. People become far more aware of a streaming service they don't use because of the experience of having to load and unload the app, or more aware of the streaming services they DO use most often because of loading and unloading the app.
Creating a seamless experience to access streaming services could work in favor those streamers that are less popular. It's the old experience of having to go to the butcher, the baker, the grocer compared to the modern experience of going to the Supermarket, even if that Supermarket is Wal-Mart or Target, and we do have room for at least ONE extra stop like a Costco, while Sam's Club is facing some problems.
After some time, the TV landscape may just go back from where it started.