Sony Mobile is preparing derived models from the Xperia Z4, the obvious units being the Xperia Z4 Ultra and Zperia Z4 Mini. Of course, the latter has all the odds of being a “Compact” unit actually. Codenames related to these phones have appeared on the Postel authority.
The codenames in question are “E5663”, “E5803”, “E6683”, “E6833” and they all passed Postel certification on April 21st. It appears the devices are made in China and the E series units are associated to high end smartphones. The D58xx models are the Xperia Z3 Compact units, so the E5803 may well be the Xperia Z4 Compact. The E6683 and E6833 are also higher end phones, that could be turned into the Xperia Z4 Ultra and a version of the Z4.
Sony Xperia Z4 was announced yesterday in Japan, with a Full HD 5.2 inch screen, but there are rumors that a Quad HD version will be released internationally. Postel is a certification authority of the Indonesian government and their information is reliable. If you allow us to speculate using older rumors, I’m pretty sure the Xperia Z4 Ultra will be a Quad HD model and the Xperia Z4 Compact will adopt at least a Snapdragon 805 CPU, if not Snapdragon 810.