It looks like Sony is jumping on the Android M development bandwagon forthwith. They just announced that the Android M Developer Preview will be available on nearly all of their Xperia devices soon. They also shared plans to release a test build of Android M for Xperia products in the Sony Open Device program.
If you plan to try these out, keep in mind that these developer previews are not meant to be your permanent (daily driver) OS. The modem and camera are non-functional. Still, for any of our devs out there, this gives you the opportunity to test out your apps on Sony Xperia devices.