Overall, as we already said, the Z4 looks a lot like the Xperia Z3, though some subtle changes are clearly visible - including the larger front-facing speakers which have a slightly different position than on the Z3.
It's said that the Z4 measures 146.3 x 71.9 x 7.2 mm, which means it's almost the same size as the Xperia Z3 (146 x 72 x 7.3 mm). Thus, we're expecting the new handset to sport a 5.2-inch display. It's not clear if Sony will use a 1080 x 1920 pixels, or a 1440 x 2560 pixels panel, but it might go with both variants.
The Xperia Z4 will definitely run Android 5.0 Lollipop, while other features are expected to include Qualcomm's octa-core Snapdragon 810 processor, a 20.7 MP rear camera with Sony's new IMX230 sensor, and 3 GB or 4 GB of RAM. We're pretty sure that Sony will include other novelties as well, but for now that's all we know. The Z4 should be officially announced and launched sometime this summer. Interested?
Alleged Sony Xperia Z4 (non-final) renders
source: Nowhereelse (translated)