Windows 9 will likely arrive in Q2 or Q3 2015.
Just days ago, document leaker FaiKee revealed that the preview version of Windows 9 would arrive either on February 3, 2015 or March 2, 2015. That seemed to coincide with the release schedule of Windows 8, which saw the current OS in a Consumer Preview build back in February 2012.
MyCE now adds to that report, using the same leaked document, but fewer edits. According to the info, Windows 9 is actually in an alpha state, and a Preview build will be released in Q2 or Q3 2015, not in February or March. The cloud-based Windows 365 is also supposedly in alpha and based on the Windows Core.
Office 2015 is listed as Alpha-TP-CP1 on the document, meaning Technical Preview and Consumer Preview 1, which indicates that the next Office could soon appear as a public preview. Also possibly appearing soon is Office 2013 Gemini, the Modern UI touch-based apps for the Office suite. These are listed as RTM and may launch in Summer 2014.
Also on the leaked document are "update items". These include changes to the modern UI interface, Windows Defender, Windows Activation, OneDrive and Cortana, the Digital Assistant making her debut on Windows Phone 8.1. Cortana will likely be embedded in Windows 9 as well, as Microsoft is currently looking for a software development engineer to help develop the next generation of Microsoft's Digital Assistant.
The leak also reveals that Windows 8.1 Update 2 is in the preview stage, meaning that customers could see the update in mid-2014. Previous reports have pegged the window between August and October: it's anyone's guess at this point (save for Microsoft). This update may bring back the Start Menu, which will combine the old-school listing with flashy new live tiles.
Finally, the leak shows that Windows Phone 8.1 has gone RTM (Release to Manufacturing). The document also shows that Windows Phone 9 will make an appearance in Q2 to Q3 2015. However, as always, take all this as rumor and speculation.