T-Mobile has had a very good past few years, marking an upswing from near-certain death. Their parent company, Deutsche Telekom, has even decided against selling them off. Instead, T-Mobile may be the ones doing the buying, or may merge with one of their contemporaries, according to Morgan Stanley. T-Mobile has already wielded considerable influence over the mobile industry, mostly by forcing change, and it seems that they are now in a position to bring about even more changes. Rather than trendsetting, however, T-Mobile's influence this time around could come from sheer size and power. The "Duopoly", as T-Mobile CEO John Legere calls AT&T and Verizon, could face a serious threat to their dominance of the US mobile space going into 2017.
The biggest way T-Mobile could make waves would be by merging with Sprint. The two of them, hand in hand, would form a massive network. Refarming spectrum that they both own toward the goal of forming a single network could easily result in a large and robust LTE network, and Sprint's wealth of high-band spectrum combined with T-Mobile's deep pockets and wide LTE network practically guarantee that the duo would dominate the 5G world early on, and that dominance could continue, given proper capex and buildout.
Merging with Sprint isn't the only path to the top that T-Mobile has available, of course. They could also merge with a small cable or telecom provider, gaining valuable spectrum and the ability to begin competing with the bigger carriers in the area of owned media, rather than relying on Binge On. Buying up a smaller carrier, such as US Cellular, is also an option; folding US Cellular's network into their own would provide a huge boost in subscriber count and network capacity, among other benefits. With cable companies looking to get into the wireless business, of course, T-Mobile could always woo a big name in cable and shake up the industry that way. It's entirely possible that T-Mobile will continue to forge on alone, even with all of these options available to them. Needless to say, the whole industry is watching them closely to see what choice they end up making.