Just after we reported that Sony's next flagship phone received certification in Japan, an unknown smartphone from Sony passed through the United States' Federal Communications Commission (FCC). The official documents reveal that the device will support LTE bands 2, 5 and 7, which could also be supported by a mid-range model. The firmware's build number is also mentioned (25.0.A.0.33) and is higher than the expected number of the upcoming Lollipop update for the current Xperia Z3 (23.1.X.X.XXX): that also isn't enough to convince us, since Sony's firmware numbering has often been confusing in the past, with a higher build number not always indicating a flagship model. However, the timing of this approval is convincing enough to speculate that this could indeed be the Xperia Z4.
Currently, it's expected that in addition to the Xperia Z4 the Japanese manufacturer will also release its Compact and Ultra versions, all featuring the same 64-bit octa-core Snapdragon 810 SoC from Qualcomm with its powerful Adreno 430 graphics and LTE Cat.9 (450 Mbps) support, 3 or 4 GB of RAM (depending on the region), a 20.7 MP rear camera with an updated sensor and a 5 MP front camera. IP68 dust and water protection will be used and it appears that Android 5.0 Lollipop will be installed right away. The expected battery capacity for the "normal" Xperia Z4 is 3400 mAh. Additionally, some sources now claim that two versions of the Xperia Z4 itself might be released, both equipped with a 5.2-inch display but differing in resolution: a 2560x1440 screen will be offered to compete with Samsung's and HTC's new flagships while a 1920x1080 (which is still very sharp) option will satisfy the customers more keen on higher graphical performance and longer battery life than more pixels.
Sony has not commented on any of the rumors yet, but with the MWC exhibition in Barcelona only 6 weeks away, it won't be long until we will finally know how many versions of the Xperia Z4 will be introduced.