A leaked image from a Microsoft intranet site has disclosed that Office 2016 for Windows will be released on September 22.

Office 2016 for Mac is already available to Office 365 subscribers. When that was launched in July, Microsoft said that regular retail copies would be released in September. While we're not certain, it seems likely that September 22 will be the release date for that, too.

Office 2016 is an incremental update. It makes styling between Windows, OS X, and the mobile apps a little more consistent—by default each app gets a boldly colored title bar that reflects the icon color, just like the mobile apps—and includes improved collaborative editing, rights management, and data analysis capabilities.

The leaked image also says that the new Office 365 variant, E5, and Skype for Business are due in "Q2." With E5 already promised by year-end, this likely refers to the second quarter of Microsoft's financial year (October to December 2015) rather than the second quarter of the calendar year (April to June 2016).

Office E5 replaces the old E4 plan. E4 is the most pricey tier of Office 365 for enterprises at $22 per user per month when bought on an annual basis, and it includes the full desktop Office suite, Exchange, SharePoint, Skype for Business, Business Intelligence, and Rights Management support. It also supports PBX integration for Skype for Business, but this requires an on-premises server.

The new E5 will offer a new cloud-based PBX capability, which is currently available to US customers on a preview basis. With this, businesses will be able to use Office 365 for virtually all of their (non-hardware!) IT and infrastructure needs, and they will have one less reason to operate on-premises infrastructure servers. E5 will also include upgraded data analytics and security capabilities. Pricing for E5 is as yet unannounced.

The image also says that on-premises servers will follow those Q2 releases. SharePoint Server 2016 received its first public preview yesterday; this is also due for a Q2 release, but this time, it's the calendar year. Exchange 2016 has been in public preview since July.

Pricing for Office 2016 hasn't been announced, but it's likely to be in line with the Office 2013 prices.