That's, in essence, what I've seen reported, too. Plus, considering there are few new listeners actively seeking out radio, building another form of radio, especially in the U.S., there would be no motivation for commercial broadcasters to somehow band together to invent such a new form. DAB in Norway was a government initiative. The government doesn't run broadcasting in the U.S.
Honestly, I don't understand this frequent theme that keeps resurfacing in Radio Discussions, that somehow AM or FM OTA radio will be, or should be, shut down by the government. As with my comment about DAB migration being a government initiative in certain countries, such a structure doesn't exist in the United States. Any decision or process to abandon operating a radio station is made by the individual licensees of the station, not the government. Unlike UHF-TV spectrum, since the AM and FM bands are no good for any other use, there's zero interest in having broadcasters vacate those bands.