It looks like the Nexus owners will not be the only folks who get to try out the Android N Developer Preview early. Sony has released it for consumers to try it out on specific Xperia Z3 models. The Android N Developer Preview for Sony devices will only work on the D6603 and D6653 models of the Xperia Z3.

Here's a breakdown of the steps if you have one of these devices and would like to try out Android N Developer preview on it:
  • Connect your compatible Z3 device to a computer with a USB cable.
  • Xperia Companion will open automatically
  • Make sure you have Xperia Companion version 1.1.24 or later. If not, download the latest version from here.
  • Hold down the ALT key on your computer and click on Software repair on the home screen, then follow the guide.
  • You’ll be asked to disconnect and turn off your device, then to reconnect whilst holding down the volume down key to start the software flashing.
  • You can return to factory settings at any time by connecting back to Xperia Companion and following the Software repair

For more info, here's Sony's landing page on the subject: Android N Developer Preview – Xperia Z3 Series | Sony Developer World