The awkwardly named Windows 8.1 Update 1 release earlier this year inspired speculation that Microsoft might produce a similar major group of "Update 2" enhancements for Windows 8.1 ahead of the expected Windows Threshold release . Microsoft has now made it clear that won't happen: we'll see small changes to Windows 8.1 as part of the monthly patching cycle, but nothing else.
Microsoft spelled out that approach in a blog post today:
Rather than waiting for months and bundling together a bunch of improvements into a larger update as we did for the Windows 8.1 Update, customers can expect that we'll use our already existing monthly update process to deliver more frequent improvements along with the security updates normally provided as part of "Update Tuesday." So despite rumors and speculation, we are not planning to deliver a Windows 8.1 "Update 2."
The next scheduled Patch Tuesday update -- it's going to take some adjustment to call it Update Tuesday -- is next week (and will happen Wednesday in Australia because of global time differences). The changes to Windows 8.1 Update are fairly minor in that release: enhancements to touchpad interaction, updates for Miracast, and changes to SharePoint login behaviour.
Windows 8.1 Update is now the mainstream release; as of June, Microsoft is no longer patching Windows 8.1. There's no official date attached to Threshold; it's rumoured for a 2015 release.
August updates for Windows 8.1 and Windows Server 2012 R2 [Windows Experience Blog]