Comment by Myself5 from XDA- Developers:
If someone here would be able to read the Android Sourcecode, they would know why the Z3 and other msm8974 devices are no longer officially supported.
With 7.0.0, all msm8974 code was removed from AOSP. After all, what you expect is that Sony is supporting a no longer AOSP supported chipset. At what point is that a fair assumption?
Of cause its sad to hear that the Z3 got the N Previews and now is no longer supported, but guess why there was no Preview 4 or 5 either? Probably that was around the time when Google gave the 8974 chipset the boot.
After all, the article is not really well researched in my eyes, and written like its Sony’s fault that the 8974 platform is no longer supported. Of cause up to some point it is. But there is also a greater matter, which is not in the hands of Sony at all.
BTW, Sony’s Open Devices program will probably find a way sooner or later, its just not something the company can do officially IMO.