At this time, Nexus 5 is the only one as Android device that is running with native working version in the wild of Android 4.4 Android. If you think that you want to jump on Android 4.4 KitKat, it is possible for you because various custom ROMS could jump to your rescue. Well, check this post to know about the devices that works for KitKat below.
As it has been announced by Google that Galaxy Nexus not only has hardware capability to work with new operating system but it also will not get an official upgrade for Android 4.4. The rumors said that the reason could be about Texas Instrument that does no longer provide support especially for OMAP chipset which is found in the device. About the announcement, it caused the developer to rise up with the challenge of three different versions. SlimKat and also A Taste of KitKat are Android 4.4 ROMs that are available from XDA Developers forum while Shiny is available from RootzWiki. However, these ROMs do not always fit for Galaxy Nexus.
There is AOSP ROM around RootzWiki for Nexus 4 and the biggest one is Google Experience Launcher is not included in AOSP file. However, it is expected to be added for a later date so it should be a simple installation as installing APK file. You will need rooted Nexus and flash a the file to keep it working. Check here if you need help
Thanks for RootzWiki that at this time you can get Nexus 4 AOSP file to update Android 4.4 on Nexus 7 WiFi version. You can download and flash AOSP file to your Nexus 7. Check the RootzWiki for Nexus 7 (2012) and Nexus 7 (2013).
There is an alpha version for SlimKat ROM that could be flashed to the device. Check out post over at the XDA Developers forum.
Sony Xperia Z
Through XDA Developers with 4.4 Android ROM for this device, it is working. Check the downloading link and instruction over at this post.
Android 4.4 ROM for this device is specifically for T-Mobile version for Moto X. it does not include Google Experience Launcher. Check the following post over XDA Developers Forum.