Sony kind of announced the Z4 a few months ago, but now it's moving quickly toward a do-over with the Z5. There will actually be three phones called Z5, which could be announced in a few days at IFA. You don't have to wait, though. A video from the French site Clubic was leaked showing off the Z5 in moderate detail.
There will apparently be three phones in the Z5 family—Xperia Z5, Xperia Z5 Compact, and Xperia Z5 Premium. The main difference between these phones will be the size and screen resolution. According to the video, the high-end Z5 Premium will have a 5.5-inch 4K LCD. Yes, really. A 3840x2160 smartphone, which works out to over 800 pixels per-inch. The regular Z5 will be 5.2-inches and the Compact is 4.6-inches. It's not entirely clear, but these will probably be 1080p and 720p screens. The regular and compact leaked before too.
All three phones will share a new fingerprint sensor on the power button, a 23MP camera, and two days of battery life. With a 4K screen? I'll believe that when I see it. The video also seems to confirm the Snapdragon 810 is going to be powering all three devices. This is all based on alleged fan translations of the video—I'll have our resident French speaker check the video as soon as she's conscious. We'll know for sure what's what when Sony (probably) talks about the Z5 at IFA in a few days.