DESIGN
So let's first talk about it's design. It has thin bezel omni-balance design. In the pictures we can see that Xperia Z4 has very similar design language as previous year's Z3. According to the @onleaks, the Xperia Z4 will measures 146.3 x 71.9 x 7.2 mm. Sony made some minor changes to the buttons like the Sim slot now changed from right to left and the SD card is also seem to be missing.
The USB now moved from the top left where it was covered with the flap to the bottom of the device and now it is completely exposed. Xperia Z4 also gets the new wider look speakers placed on the top and bottom edge of the device. Seems like Sony may use Boom Sound speakers for the Z4.
This time we are not sure about the waterproofing of the device as many ports are esxposed but we can say for certain until Sony make it official.
DISPLAY
The new Z4 will packs a 5.5 inch QHD display. Although Sony says that they don't beleive in QHD displays as they consume more power. The previous Z series flagships packs the FHD display but at that time they were the best displays any smartphone packs. But now time has changed and mostly all the companies are now switching to the Quad displays.
The recent leak suggested that the Z4 comes in two models. One with Full HD display and other with Quad HD display.
PERFORMANCE
The new Xperia Z4 will now boasts more powerful 64 bit Qualcomm Snapdragon 810 octa core processor which may comes with 4GB or 3GB of ram and 32GB of onboard storage. On the other hand we also have a leak via GeekBench which gives some idea about the specs.
Xperia Z4 received a score of 1196 for single-core performance and 3576 for multi-core which are slightly better. In the terms od connectivity the Z4 will features a Category 6 LTe and Bluetooth 4.1.
CAMERA
It sports a faster 21MP new Exmor RS IMX230 sensor which stacks CMOS Image sensor which brings high speed AutoFocus, better performance in HDR mode and also higher level of detail in HD videos. It is capable of recording 4K resolution (4096x2160) video and shoot videos much like much like it take a normal photo.