Sony Xperia Z3 Series devices
Sony Unveils New Z3 Series Xperia Smartphones, Tablet, Smart Wearables at IFA 2014Sony Mobile

Sony hasn't officially announced the release date of its upcoming devices - Xperia Z4 and Xperia Z4 Ultra – but several reports have claimed that they would be unveiled at the upcoming Consumer Electronics Show 2015 (CES 2015) to be held on 5 January at Las Vegas.

The Japanese electronics giant could also unveil the Xperia Z4 and Xperia Z4 Ultra at the Mobile World Conference 2015 (MWC 2015) to be held a month later but the company has scheduled a conference at CES 2015, giving a strong hint that the devices could be announced at the event. The devices are likely to be launched a few weeks after the unveiling event.

Sony is also expected to announce more mid-range Xperia phones and tablets at the CES 2015 besides the Xperia Z4 and Xperia Z4 Ultra.

The company is yet to reveal the specifications of the Xperia Z4 and Xperia Z4 Ultra but several websites have revealed them.

According to latest report by Phone Arena the Xperia Z4 will sport a 5.4-inch Quad HD Triluminos display and powered by a Snapdragon 805 processor. It is expected to come packed with 4GB RAM, run on Google's recently released software Android 5.0 Lollipop, have a 20.7MP main camera and 4.8MP front snapper, and a 3420 mAh battery.

The report contradicts earlier claims that the device would sport a 5.5-inch screen display and powered by a Snapdragon 810 processor. It will take on devices like the recently released Apple's iPhone 6 and yet-to-be-released Samsung Galaxy S6 and HTC One (M9) that are likely to be unveiled in the first quarter of 2015.

The Xperia Z4 Ultra is said to sport a 5.9-inch Triluminos display, powered by Snapdragon 805 chipset, and memory packed with 4GB RAM. Its camera is said to be 16 MP with dual LED flash and a thin chassis measuring 5.7mm.