Sony Vice President talks about the Xperia Z4 smartphone, says the Z3 series is still doing very well

Speaking of the Z3, Tim Harrison says that the entire Z3 series (including the 5.2-inch flagship model, the Z3 Compact, and the Z3 Tablet Compact) is "doing really well in the market, and there is still quite a considerable amount of interest in those particular products."
"The innovation is not so much about launching and announcing a flagship with more and more megapixels and so on, it's about how can you make consumers' lives more innovative and more relevant as we go forward. [...] We will continue to launch beautiful hardware but it's not the only thing anymore. The story is beyond that. It's whether you are expanding consumer experiences beyond a technology standpoint, making sure these experiences are available to as many consumers as soon as possible, even to those who bought products six months ago," said Pierre Perron.
The bottom line is that, for now, Sony can't tell us when the Xperia Z4 will be released, but it's likely that this will happen in the summer - just as previously rumored. The new flagship smartphone should be powered by a Snapdragon 810 processor, and might have to versions: one with a 1080p display, and another one with a Quad HD (1440 x 2560 pixels) screen.
sources: Trusted Reviews, The Inquirer via Xperia Blog