Xbox One Controller ‘Preview’ Firmware Solves Disconnection Woes, Reduces Connection Time
The latest preview build, OS version 1502.150120, addresses two main issues, the first being a faster connection time. Prior to the firmware, it could take an Xbox One controller 4-5 seconds to connect when powering on, and that time is reduced to about 2 seconds after applying the update.

Secondly, Microsoft promises stability improvements.
"The firmware also provides a number of fixes that address issues submitted by customers and preview participants," Microsoft said.
We'll have to wait and see if the new firmware solves the problem en masse once it trickles out of the Preview Program and into the hands of regular users. In the meantime, if you're experiencing disconnect issues with your Xbox One controller, there are a number of troubleshooting steps you can try -- they're outlined in this support document. But if none of those steps work, we'd advise on waiting for the firmware before requesting an in-warranty repair or replacement to your Xbox One console or controller.