Xperia Z3+ might be the name of the global variant of the Sony Xperia Z4. At least, that is what a Sony leaked document hints.
A week ago, when Sony Mobile quietly launched the Xperia Z4 in Japan has also introduced several accessories to expand the user experience, including a Style Cover Window identified as model number Sony SCR30.
A whitepaper of the aforementioned accessory published and soon after withdrawn by Sony from its website, reveals some interesting information, that the Xperia Z4 will also be known/marketed as Xperia Z3+, which might be the variant the OEM intends to sell globally as of this summer, otherwise why would it remove it? (below a screen capture making reference to Xperia Z3+ name, before Sony removed the paper from its website).