We recognize that many Insiders will be disappointed to see their device is no longer supported. We looked at feedback from our Windows Insiders and realized that we were not providing the best possible experience for our customers on many older devices. That helped us determine which devices we support for the Windows 10 Creators Update. We are continually listening to your feedback to provide the best experience for ALL of our customers.
At some point, users of these unsupported devices were a victim of their own success, so to speak. The testing provided by the Windows Insider program showed that these older phones were not performing as well, most likely with a higher rate of bugs and crashes, and so they have been culled from the list.
Users of these older phones will be able to keep using the latest build available to them (15063.138), but these phones won’t be updated or supported from here on out.
Tough news for some, but to be honest it’s understandable.