New screen shots shared by Windows leaker "WZor" on January 8 indicate Microsoft's progress on an update to Windows 8.1 due out this spring.

Back in October 2013, I blogged about the coming Windows 8.1 Update 1 release -- an updated version of the Windows 8.1 operating system. According to my contacts, Microsoft is/was planning to deliver this update around the time it releases its Windows Phone 8.1 "Blue" operating system release. The goal of Windows 8.1 Update 1 is to bring the PC/tablet and phone operating system platforms into closer alignment, from a programming interface standpoint.

WZor's new screen shots don't show any new features and he has not shared any leaked Update 1 bits at this point. He says that Microsoft's "golden" OEM partners will be getting confidential test builds later this month. It sounds as if no public preview is planned for the Update 1 release.

WZor's accompanying blog post (translated from Russian) indicates that Microsoft is planning to release to manufacturing (RTM) Update 1 in March and make it publicly available as of April 2014 as a free upgrade for all Windows 8.1 users via Windows Update. He also claims that MSDN and Microsoft volume licensees also will get the RTM bits by late March or early April.

Not so coincidentally, Microsoft's Build 2014 developer conference is set for April 2 to 4 in San Francisco.

It's still unclear whether Windows 8.1 Update 1 will include tweaks to the user interface of Windows 8.1, including t he return of some kind of "mini" Start Menu or whether Microsoft will introduce a new Start Menu at some future point. My sources have indicated that the Windows team is looking for ways to make Windows 8.1 friendlier for mouse and keyboard users (huzzah!) and that the return of some kind of Start Menu, along with the already introduced new Start Button, is in the cards. I'd be surprised if the Start Menu is part of Windows 8.1 Update 1, however.

It's also not clear to me (yet) whether there will be additional Windows 8.1 update builds delivered throughout 2014. The Windows team is working on a new version of Windows, codenamed "Threshold," which is expected to debut around the spring of 2015, according to my contacts. Threshold may ultimately be christened "Windows 9," some have suggested. But I'm wondering if there might be Updates 2, 3 and/or 4 to Windows 8.1 on the roadmap....

Microsoft officials are not commenting on any operating-system futures, in case anyone was wondering.