Microsoft is working on expanding its Windows 10 for phones preview build to include Windows Phones that are not under the Lumia brand, but details about when this will happen have not yet been revealed.
This move was revealed by Windows Insider head Gabriel Aul on his Twitter feed in response to a question on that very subject. He stated:
"We're working on other devices as well, but don't have news to share yet."
The current build of Windows 10 for phones is supported only by six devices: the Lumia 630, 635, 636, 638, 730 and 830. Late on Friday, Aul wrote a post on the Blogging Windows site announcing that the next preview build will be supported by 36 smartphones, all of which will be Lumias. There's no word on when that build will be released.