We already have evidence of stations in some markets that have a dozen SD streams or more on a single carrier. Most stations that opted out of the reverse auction or didn't qualify are looking to buddy up with someone else's existing complement of channels. They have a choice: stop carrying channels or divvy up the existing bandwidth even finer.
Of course what probably needs to happen is many of the diginets need to consolidate to eliminate overlap.
If you believe the Next-Gen rhetoric, the bandwidth usage may only be 30% of what DTV requires so they'll have to drive a wedge about that big into each market or decide not to simulcast them. While they're trying to figure that out, there's going to be more double-digit subchannel "lighthouse" stations or trying to fit perhaps three HD streams on a single channel (two already shows a noticeable impact).
From the accounts of those who have experienced them, you have to be a glutton for punishment to watch a DTV station that offers almost double what they thought could theoretically be done in terms of subchannels.
None of those stations with a dozen SD streams is carrying a major network.
Here's a real-world example of how the ATSC 3.0 transition is working:
Phoenix, my home market, is currently testing this very thing. There are 12 full-power stations in Phoenix, and ten of them are owned by companies participating in the the ATSC 3.0 test bed: Meredith (KTVK, KPHO), Scripps (KNXV), TEGNA (KPNX), Nexstar (KASW), Fox (KSAZ, KUTP), Univision (KTVW), NBC/Telemundo (KTAZ), and Arizona State University (KAET). In addition, Univision also has a Class A station, KFPH, that is participating. The 11 participating stations program 39 subchannels. Class A KFPH 35 was chosen to be the ATSC 3.0 test station. It carried four subchannels; Unimás 35 on 35.1 (1080i), Univision 33 on 35.2 (1080i), getTV on 35.3 (480i) and Escape on 35.4 (480i). The other stations split its subchannels - mostly. Full-power KTVW 33 was already carrying Univision 33 on 33.1 (1080i) and Unimás 35 on 33.2 (1080i), so the one duplicate stream of Univision on 35.2 went away and the duplicate stream of Unimás on 33.2 now is identified both as 33.2 and 35.1. KPNX 12 took getTV and labels it as 35.3, while KNXV 15 took Escape and labels it as 35.4.
In other words, you don't see two stations partnering to implement NextGen; you will see several station groups. Eight already belong to the Pearl TV consortium - Meredith, Scripps, Tribune, TEGNA, Nexstar, Cox, Raycom and Hearst - so you will get cooperation among those groups already, and Fox, Univision and NBC/Telemundo are willing participants as well. That's a major group of owners, plus I'm sure when the time comes, CBS and ABC O&Os will step up as well.
Add to that numerous LPTV stations that can provide additional hosting capabilities. WatchTV in Portland has been a leader in ATSC 3.0 testing, and Edge Spectrum Inc. (ESI) with hundreds of LPTV stations nationwide is committed to ATSC 3.0, even hiring away WatchTV's Chief Engineer, Jess Ortega, to become ESI's Chief Technology Officer.
With full-power station groups and LPTV owners participating, you're not likely to see a dozen or more programming streams on a single ATSC 1.0 station, unless they already had it to begin with, and certainly not on a station that is carrying a major network. Univision and Unimás employ multiplexers that handle two 1080i streams well, even when both networks are televising fútbol matches, so I don't see the gloom and doom scenario that you're putting forward. If there is a big squeeze on ATSC 1.0 programming, it will be at the very end of the transition, after the FCC-imposed five-year requirement expires that requires stations to duplicate ATSC 1.0 programming on ATSC 3.0, and station owners nationwide have abandoned ATSC 1.0. By that time, ATSC 3.0 television sets will be abundant and affordable, and there will be no excuse for even the most parsimonious to not invest in a new TV.
