Update to my last post:
The owners of channels 2, 4, 13, and 30 have all said they would be upgrading to ATSC 3.0 this year. Channels 5 and 7 probably will as well, but they haven't publicly said anything on the subject. However, as of 2/17/2020, nobody has submitted an application to do so. So, we'll see.
I'm guessing that means one station will upgrade and the other three will put their 3.0 signals on that one station. Meanwhile, the subchannels from the one station that actually upgrades will be split among the other participating stations.
That seems to be the plan in other markets.