“This isn’t a case of going from four to three wireless companies — there are now at least seven or eight big competitors in this converging market,” John Legere, T-Mobile’s chief executive, who would become the combined company’s leader, said in a statement. He said that the industry is in a mash-up with cable players like Charter and Comcast that are trying to get into wireless, and that AT&T is now the largest TV provider in the country.

It is true that the wireless and cable industries are likely to continue to transform over the next decade, but it is far from clear how the market will be divided. The efforts by the cable companies to get into the wireless game are nascent and, at least so far, unproved.

For better or worse, regulators generally make their assessments based on the current marketplace; they are not prophets.

Part of T-Mobile-Sprint’s argument is that the combined company could rapidly deploy the next generation of wireless technology, known as 5G, and that its progress in that area would force AT&T and Verizon to move faster.

“Only the combined company will have the network capacity required to quickly create a broad and deep 5G nationwide network in the critical first years of the 5G innovation cycle — the years that will determine if American firms lead or follow in the 5G digital economy,” the companies said in a statement.

They also suggest, perhaps trying to align themselves with President Trump’s jobs agenda, that the merger would create more, not fewer, jobs.

But many analysts are not convinced.

“I don’t think that is credible,” Craig Moffett, a veteran telecommunications analyst from the firm MoffettNathanson, said of the claim about jobs. “And AT&T and Verizon are going to do 5G anyway.”