There's no way to know what to expect from Sony smartphones anymore. According to their 6-month renewal cycle, we should've had a new flagship last March, but the company waited a little longer to introduce the Xperia Z4, being an exclusive smartphone for Japan. When compared to its predecessor, the changes are really hard to notice, as the design stayed pretty much the same with very few differences, and Sony is actually selling the Xperia Z4 under the Xperia Z3+ name outside of Japan.
The Xperia Z4 is slimmer and lighter and the micro USB port is now exposed while keeping the IP68 certification making it dust proof and water resistant, this is the reason why there's not a charging port for the magnetic dock, making the design a little cleaner. Other changes include the design of the front-facing stereo speakers, which have been moved to the edges of the device making them less noticeable but the camera in the front has moved to the opposite side and is now a little bigger since it increased the resolution of the sensor to 5 megapixels. But that's about it, the screen is not only the same size as the one of the Xperia Z3, but it also kept the same Full HD resolution.
On the inside, the Xperia Z4 uses the newest high-end processor from Qualcomm, the Snapdragon 810 and the internal memory has increased to 32 GB, although it still can be expanded with Micro SD cards. The battery is actually a little smaller, but the company claims that with the battery-saving modes, it can give enough power to last for two days under normal usage. Now, the exact launch date of the Xperia Z4 has been given for the Japanese carrier SoftBank, June 12. It can be preordered right now in one of its four different colors (white, black, copper or aqua green) at a price of 81,120 yen (around $646). While this carrier was the third one to announce the availability of the device, there's no word on the launch date or price with au or NTT DoCoMo, although it is expected to launch in the next few weeks with the last one.