A new speculation aimed at Sony's upcoming rumored flagship, Xperia Z4, has surfaced online. Previously, the device was thought to launch at this year's International Consumer Electronics Show, but not even its shadow has turned up in public.

This time, Air Herald reported that the smartphone may arrive in two different models. Note, however, that the difference comes in terms of spec -- both will sport a similar 5.5-inch screen. According to the outlet, the Xperia Z4 will have one version packing a 1080p display, while another takes it to 1440p.

The source indicated that a 1080p screen has a pixel density of about 400ppi, while a 1440p display houses around 534ppi.

However, an earlier note from Android Pit cited another report, which claimed that Xperia Z4's QHD version will only be sold in the United States. That means the rest of the world may not get Z4's clearer variant.

It is also worth noting that Sony could be paying special attention to music lovers, through another alleged version of the Z4. Trusted Reviews took note of iGeek's report, which revealed that the company is conceptualizing a "a music-focused 'Walkman' variant" of the upcoming Xperia smartphone.

The outlet commented that the variant appears to be a slim Xperia Z3 that "runs an app mimicking the classic Walkman interface."

As told by Android Origin, the Xperia Z4 may pack Qualcomm's Snapdragon 810 octa-core 64-bit chipset (clocked at 2.8GHz), along with Adreno 430 GPU. Other rumored specs include 4 GB of RAM, 32 GB of internal storage, LTE Cat.6 connectivity and Bluetooth 4.1.

In terms of camera, we may have to look back at Sony's announcement earlier in November, focused on its newest smartphone camera sensor called the Exmor RS IMX230. The system sets to ship in April this year.

In addition, the company brands the sensor to be the industry's first, packed with an "onboard image plane phase detection AF signal processing function." Simply put, the technology helps users capture excellent images even if the subject appears to move quickly.

Since Lollipop is on its way among top Android devices, Android Pit predicted that the Xperia Z4 could get its latest version upon release. The source added that the handset could retail more expensively than its predecessor, which sells nearly $600 as of press time (via Amazon).

The device is now expected to launch at the Mobile World Congress, dated Mar. 2 - 5 in Barcelona, Spain, wrote Trusted Reviews.

Check out adrianisen's clip of an Xperia Z4 concept below.