The main argument against the proposed T-Mobile and Sprint merger is the possibility of reduced competition; After all, Canada has three major carriers, and has not done so well for the country. The United States Department of Justice is only curious about whether this company will sell enough wireless spectrum for a new independent carrier to work, and the most recent company to show interest is Dish Network.
According to Bloomberg, cable company Dish Network is on talks to buy both Boost Mobile (Sprint's NVMO brand) and wireless spectrum owned by T-Mobile and Sprint. Buying allows T-Mobile and Sprint to move forward in a merger, since approval from the Department of Justice is one of the few remaining roads. The Amazon was also reportedly interested, but it is not clear if the case is still there.
Ironically, T-Mobile is a cruel critic of the Dish spectrum hold over the years. T-Mobile CEO John Legere said this year's food, saying a tweet "They have changed the $ 11B spectrum over the years and have not taken every deadline deadline." The company also wrote a letter to the FCC asking that the Dish spectrum should be relicensed.
The dish floats the possibility of building a 5G network with its existing attachments, but the company is also looking for someone to purchase the ~ 100 MHz full spectrum. However, major carriers are unlikely to be interested in what Dish owns, especially after the recent FCC auctions.