How long can T-Mobile keep its Un-carrier momentum up?

Given T-Mobile's track record, there's no surprise that it's led the industry in growth. The question is how it will keep the engine going at the same pace.

The fourth-quarter report for the nation's third-largest wireless carrier included a forecast for branded postpaid net customer additions of 2 million to 3 million, down from 2017's 3.6 million tally. T-Mobile has traditionally been conservative with its  projections, but the figure suggests that some of its momentum might be ebbing.  

In January, T-Mobile got things rolling with the early release of its fourth-quarter customer numbers, which include 1.9 million total net additions and 891,000 of the critical postpaid phone subscribers, or people who pay at the end of the month and are considered the most valuable customers. 

But a look at the full results shows that its dominance over the industry faded a bit. T-Mobile has typically outstripped the other three players in growth, but in the postpaid phone category this period, Verizon added 431,000 customers, AT&T nabbed 329,000 and Sprint signed up 184,000. 

That T-Mobile's rivals are edging closer speaks to the competitive stakes that have pinned down the industry. The latest incentive to switch has been with video: AT&T throws HBO into its plan, T-Mobile bundles Netflix and Sprint offers Hulu , in addition to streaming music service Tidal. And like T-Mobile, the numbers from all of the carriers suggest a general slowdown in industry growth as consumers stick to their respective carriers. 

So for T-Mobile, what's next?

To be fair, the industry has continually asked the company about its next move ever since its Un-carrier campaign kicked off nearly five years ago. And while not every Un-carrier announcement was a smashing success, T-Mobile does enough -- elimination of contracts and phone subsidies, free international data, going all-in on unlimited data, for example -- to keep making waves. 

Perhaps its next breakthrough will be with Layer 3, the video startup it acquired in December. Its move into TV comes at a time when its rivals are making huge bets in the area. AT&T owns DirecTV and is trying to buy Time Warner, while Verizon acquired AOL and Yahoo. T-Mobile said it plans to launch a service this year. 

Or T-Mobile may identify another pain point, an aspect of wireless service that annoys customers, and attempt to fix it in another splashy Un-carrier event. 

"We expect subscriber momentum to remain strong despite increased industry competition going forward as cable ramps in the space," JP Morgan analyst Philip Cusick said in a note. 

For now, T-Mobile can boast strong earnings. Like its competitors, the company benefited from the recent tax reform. The company posted net income of $2.7 billion, or $3.11 a share, compared with a year-ago profit of $390 million, or 45 cents a share. 

Revenue rose 5 percent to $10.76 billion. 

Analysts, on average, had forecast earnings of 37 cents a share and revenue of $10.83 billion, according to Yahoo Finance. The earnings projection doesn't include the tax benefit. 

T-Mobile shares rose 1.5 percent to $62.96 in premarket trading.

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