Sony has been stepping up there display game in the last few handhelds released by the company.
Sony is reportedly already in testing with some Z4 xperia prototypes with a QHD Display.
There is variants in testing at the moment with two different processors. We know one to be the Snapdragon 805 but have no confirmation on the second.

Some other differences that can be expected on the next iteration of the Xperia line is a bigger display. Info we have received has been conflicting. With half the sources claiming a 5.5 inch display and the other half claiming a 5.3 inch display.
We also have received some credible info on a new Xperia Z Ultra variant.

Stay tuned as we will be posting more on this device as it becomes available to us.