Microsoft pulls out Windows 10 for Phones preview build due to complains of bricked devices. The issue is now under investigation. Meanwhile, Lumia 940 and Lumia 940 XL could have a 3D-interaction.

Lumia device owners reported that after installing the preview build, and then trying to revert to Windows 8.1, it made their phones no longer functional.

The discussion page of Windows Insider Program said, "We are seeing some reports of failures on Lumia 520/525/526 devices when trying to roll back to Windows Phone 8.1 using the Windows Phone Recovery Tool. We are pausing build availability for these devices temporarily while we investigate the issue and work with customers who have reported problems."

Microsoft is yet to issue bug fixes for those affected. Meanwhile, Nokia Power User (NPU) cited sources that two upcoming carriers will be powered by Windows 10 for Phones. Though the names of the two devices are not yet confirmed, they are speculated as Lumia 940 and Lumia 940 XL.

It is rumored that the Lumia 940 may have a 5-inch display while the Lumia 940 XL could have a 5.7-inch display. It is also speculated that the rear camera sensor might balloon to 24-25 MP. Both are expected to have a 5 MP or even a higher MP FFC. However, what is considered to be an awesome feat is that either of the devices, or both, might have 3D-interaction, Iris scanner, a native Pen support, and possibly Hexa-core or Octa-core processors, since Windows 10 for Phones reportedly supports these chips.

U.S. designer Ryan Smalley gave a concept design for Lumia 940 and Lumia 940 XL versions. The concept included optical image stabilization and high resolution zoom, bezel-free display, aluminum chassis and polycarbonate enclosure, and rear camera covered within a polished aluminum ring. The concept also gives Quad HD 5.7-inch and 5-inch versions, Xenon flash, transparent UI, redesigned settings area, new browser, and many more. The hues are rendered in Andesite, Obsidian, and Sandstone.

Assumptions about the release date of the two devices point to early Q3, since the Windows 10 for Phones launches on the end of Q2.