Microsoft's operating systems group has decided to hold off on delivering a Microsoft-developed Start Menu until Threshold, the next "major" release of Windows. Threshold, which may or may not ultimately be called Windows 9, is expected to be released in April 2015. I'm not clear whether the postponement is because the feature won't be fully baked in time, or if there's another reason for the change in plans.
Microsoft still is moving full steam ahead with plans to try to make Windows 8.x more palatable and usable by those using mice and keyboards, as well as those used to previous Windows iterations. That strategy hasn't changed.
The new Microsoft-developed Start Menu isn't going to be the same as the Windows XP/Vista/Windows 7 Start Menus; it's expected to offer some familiarity, but also integrate Windows 8's Metro-Style Start screen concept. (For those who prefer the more traditional Windows Start Menu experience, there are a few third-party-developed Start Menus for Windows 8 on the market including Start8 from Stardock and the Pokki Windows 8 Start Menu.)
So now what's going to be in Windows 8.1 Update 2? Will there be any user-interface changes or will it be more a vehicle for under-the-covers programming interface and reliability improvements? I don't know at this point.