The first clue was at the company's recent MWC press conference, where the phone was basically shown off during a tease of upcoming Moto Mods. Recall the following photo of the forthcoming Gamepad Moto Mod. That's no Moto G5 , nor is it a mistake; it's the Moto Z 2017, newly-shaped fingerprint sensor and all.

Motorola isn't being particularly secretive about its upcoming Moto Z flagship, largely because, thanks to restrictions in its size and shape due to the company's commitment to Moto Mods, we basically know what it will look like.

And this week, Sprint and Motorola teamed up to show off the network's upcoming Gigabit LTE service in the New Orleans area. During a New Orleans Pelicans vs. Toronto Raptors basketball game (which my home team won, btw!), the carrier showed off the service to select analysts on a Motorola device running the upcoming Gigabit LTE-capable Snapdragon 835 chipset.

Here's the mystery Motorola phone coming later this year with four antennas. In a case and taped over. pic.twitter.com/vjrz3XnEAN — Diana Goovaerts (@DiaMariesbeat) March 9, 2017

As you can tell, the Motorola phone has no particular shape in that photo, as its aesthetic is being constrained by a boxy cover and tapes around the edges. A Sprint release also acknowledges the collaboration:

Motorola showcased the blazing-fast, high-bandwidth capability of a forthcoming flagship smartphone based on the Qualcomm® Snapdragon™ 835 mobile platform with an integrated Snapdragon X16 LTE modem, supporting Gigabit Class LTE.

Sprint says that it used a combination of "three-channel carrier aggregation and 60 MHz of Sprint's 2.5 GHz spectrum in combination with 4X4 MIMO (Multiple Input Multiple Output) and 256-QAM higher order modulation to achieve incredible Category 16 LTE download data speeds on a TDD network." In other words, the carrier is finally making good use of its extensive high-band spectrum — the same stuff is tried to make work on WiMAX a few years ago — for what is potentially the fastest live network performance in the U.S. right now.

Back to Motorola: device will be Moto branded. Four antennas based on "unique" tech years in the making. pic.twitter.com/ovmOymUPdJ — Diana Goovaerts (@DiaMariesbeat) March 9, 2017

Sprint says that by working with Qualcomm it plans to increase the capacity on its existing LTE network "to build a strong foundation for 5G by densifying its network with the addition of small cells and smart antennas." That's because 2.5Ghz spectrum doesn't penetrate through walls very well, and needs to be amplified using such small cells and beam-forming antennas to provide optimal performance in places like stadiums, parks and in dense urban areas.