There are a lot of rumors that the Z-series run ended because Sony is planning a newly redesigned flagship? If that's the case than it is good news, won't it? Anyway, I don't like X-Performance. To get a flagship phone around the middle of June should be 4GB of RAM. What's the point of getting a top of the line processor if the screen refreshes most of the time due to low RAM?

Adding more RAM will increase the power consumption, but the performance increment is hardly noticeable.
By balancing these 2 points, not adding RAM is a good choice.

“The Xperia Z line has reached its culmination – Xperia X series represents a new chapter and evolution of our product strategy. Whilst the Xperia Z series was all about bringing the best of Sony’s advanced technologies to smartphones, Xperia X series is based on bringing smart, adaptive Sony user experiences across camera, battery performance and hardware / software design.”

With Sony's 6 month release cycle, means the price of phone will drop very fast.
I am happy to buy older generation phone at bargain price lol.
With my phone usage pattern I don't need the most recent model anyway.
Currently using Z3C and I don't feel lag or slowness at all.