The one Nexus-style smartphone that's even bigger than the N6 is getting its Android 5.0 update today. At least a few owners of Sony's Z Ultra (nee Xperia) Google Play Edition are getting over-the-air updates to Lollipop, as evidenced by this XDA thread. Conveniently, one of those fine folks has found the link to OTA ZIP file, so you can download and flash it manually to your own phone if you don't want to wait for the rollout.
The Z Ultra is the second Google Play Edition to get Lollipop, right after the G Pad 8.3 from LG. Other devices like the HTC One M7 and M8, the Galaxy S4, and the original Moto G should be getting their updates sooner or later, though their promise of "pure" Google software has been somewhat undercut by Motorola's ultra-fast updates to its Moto X flagship.
If you're running an unmodified Z Ultra, just wait for the update message or use the usual ADB manual flash with a desktop computer. Any custom recovery or system modifications might cause the flash to fail, though at least one XDA user says he or she managed to receive the update while rooted. After flashing the update, using the existing custom recoveries to flash a new Superuser app will probably set you right again... but a backup wouldn't hurt.