Based on the screenshots it seem KDE devs tone down their interface to simpler visuals (icons, colours, shades and all the blingbling I usually associate KDE with). Is that the trend for the next iteration of KDE ? (I like it)
Yes, they have a new design project: http://wheeldesign.blogspot.fi/ Although in my opinion their work hasn't exactly been a huge improvement so far. It's just a flatter coat of paint with the same issues that already plague KDE: inconsistent padding and spacing, terrible organization (think system settings) and so on.
Also, the inconsistencies are mostly due to app developers themselves. The difference between plasma and the software compilation can exemplify that - you use two entirely different application stacks if you are developing for one or the other (qt widgets enhanced by kdelibs vs qml enhanced by plasma). And then there are multiple ways to actually develop the app interfaces - you can use anchor based widgets, ui files, or raw custom positioning which I find in reviewing a lot of codebases a bit too common for my liking.
When I have the time I try to fix it, though. The problem right now is that while the Qt world's future is QML based, the KDE applications and libraries were developed for over a decade around widgets. So when I develop something new I'm using QML and it can scale, animate, and orient really well for arbitrary window sizes and devices, but some widgets applications just anchor a toolbar to 50px indents and then it looks like puke on high DPI.
I mean you can still do that in QML, but the anchors and layouts are so easy to use it seems insane to do so.