I don't think a merger will help consumers much. TMobile capex is $5b. Sprint might spend $5b. A merged company still could have $10b, but it will take years and a LOT of money to consolidate assets. There is going to be a lot of work, and a lot of money that will not go into making the network better, but making 2 networks 1.
If you want to see a combined company make ProjectFi your carrier.
Just look at some recent mergers. Charter is doing horrible. AT&T and DirecTV brought no value but just increased TV bills. Large acquisitions tend not to benefit the customers but more so investors and those on the board who get millions for making a deal happen.
As an investor I can see the excitement, but not so much a customer.
The total percent of subscribers graph shows everything you need to know about the current US wireless industry. Verizon has ~35%, AT&T has ~35%, and all the other competitors are competing for the final 25% to 30%. This also means that 70% to 75% of all the profits are split between AT&T and Verizon which gives them the money to keep deploying and keeps them with much larger, stronger networks. If AT&T and Verizon can each afford to spend $10 billion+ on their networks each year, no smaller competitor can hope to keep up.