Image: John Legere/Twitter

If there's one thing T-Mobile chief executive knows what to, it's speaking his mind without much care for the consequences.

In a Twitter-based jibe to his wireless counterparts — specifically mobile giant AT&T — John Legere pledged as one of his New Year's resolutions to "transform the wireless industry."

Because clearly shaking it up in 2013 wasn't enough.

Legere, who has led the emerging fourth-place cellular company since September 2012, has overseen some of the biggest changes to the company — and as a result the U.S. wireless industry — in years.

In 2013 alone, he introduced a streamlined plan structure for new customers dubbed "Uncarrier," which all but killed off contracts and phone subsidies. Under his direction, T-Mobile then introduced the "Simple Choice" plan that brought into force unlimited international data roaming plans — something the wireless industry had been dining out on for years as a prime money-maker on business and international customers.

And, not content with that, the cellular giant brought out "Jump" which allowed customers to upgrade their phones twice a year — sending a clear message to Verizon and AT&T, whose policies require a two-year wait before their customers can upgrade, that such arbitrary rules were not an option. In just a few months, T-Mobile saw more than 2.2 million sign up for the service.

All at the same time T-Mobile transformed internally after its MetroPCS merger in the first half of the year. And Legere didn't even break a sweat.

Exactly what's on deck for T-Mobile in 2014 remains much of a mystery. That said, the picture Legere tweeted out suggests news coming out of the annual Consumer Electronics Show (CES) later this month, which could detail what's next in the fourth-version of its Uncarrier plans.

Also rumors spinning from last year could signal T-Mobile's next big thing: paying the early termination fees of customers wanting switching from the cellular firm's rivals. Another possible ding to AT&T, which Legere said he could "give a break... or not."

Such a move could be considered a near-death blow for T-Mobile's rivals, which would see the firm essentially pay defectors to ditch their current carrier and head to T-Mobile.

Also on deck, Legere said 4G LTE will "go faster, go LOUD," suggesting a deeper roll-out across the U.S. The next-generation speeds began a rapid expansion early last year in seven major cities, and pushed further into more than a dozen in the following months.

There was no mention or hint of T-Mobile making a punt for Sprint though. Late last year, T-Mobile's chief financial officer Braxton Carter floated the merger boat , suggesting it was "not if, but when."

"Let the transformation begin," Legere tweeted. And so it shall be.