The Xperia Z1 and Xperia Z2 are now a part of Sony's open source efforts, and unifies them with a common kernel based on the Qualcomm MSM8974 platform. This won't mean much for everyday users, since applying the software to either device means you won't be able to take pictures or make phone calls, but it will make life easier for folks who tinker with custom ROMs.
The kernel unification means developers will be able to cook something up for both devices at once, rather than needing separate ROMs for each. This is a great start, but there are plenty of Z variant models that could benefit from this AOSP treatment as well.
Head over to the Sony Xperia GitHub page to start digging around in the code. How many of you guys get down and dirty with open source projects?