Dish has been looking for a partner for its spectrum, which is particularly useful for handling 4G traffic in high-density urban areas. After Dish's Sprint bid was thwarted last year, Charlie Ergen has said he's open to a T-Mobile deal. But Sprint and T-Mobile are now eying a merger of their own (regulators permitting).
Verizon has been dealing with a 4G capacity crunch in many big metro areas; the carrier is responding by rolling out 4G in the high-frequency AWS band. Buying Dish's spectrum would give Verizon more long-term headroom.
Regulators probably wouldn't object to a deal, given Sprint and T-Mobile each have considerable high-frequency spectrum. But with Verizon having $110B in debt following the Vodafone deal, balance sheet concerns could get in the way.
The AT&T/DirecTV deal fueled speculation Verizon will make a bid to fully acquire Dish. But Verizon CEO Lowell McAdam quickly shot down the idea.