ATT nor Verizon would be able to acquire Sprint the company. But if the company goes down without being acquired by T-Mobile, let's say their customers would migrate to the remaining 3 carriers proportionally existing market shares. This outcome would be pretty great for AT&T and Verizon and strictly increase the market concentration.

Approve or not approve, regulators are sometimes forced into a position of "picking winners" :-(

Another thing that needs thinking through is what happens to Sprint's spectrum if the company goes under. What kind of rules will be placed on that auction? Would ATT and Verizon be likely winners of such an auction?