Windows will update from version 6.4.9879 to 10.0.99xx after launching this update.

Future build
This build has yet to be released, below, we write down the confirmed new features (due to leaks, announcements and reliable sources). However, some of the features listed below might not make it.

Continuum

• Continuum has been added

Desktop

• Dropdown lists have been given a revamp
• There are new animations for maximalization and restore
• Cortana is enabled by default
• The taskbar has a new design
• The search button now is a search bar by default
• New backgrounds

Media support

• System-wide support for the FLAC audio format

WinRT

• The settings charm has been removed
• Settings fly-out now appears within an app
• The titlebar has been revamped, full screen is now on the bar instead of in an option menu
• A lot of apps dropped the "Permissions" tab (when it's empty)
• Apps can be installed on an SD

Internet Explorer

• Improved support for ECMAScript 6
• Improved support for ECMAScript non-standard

Apps

• Settings has been revamped with a new interface
  
  • Multiple new settings have been added
  • Multiple other panels have been improved with more functionality, like Battery saver, Storage Sense, and more
  • Windows Update has been extended with a lot of new functionalities to replace the Control Panel counterpart
  
  
• Calculator has been revamped
• Alarms has been revamped
  
  • There is now a world clock function
  
  
• Xbox has been revamped
• Get started has been revamped
• Photos has been added as an app (not to confuse with Photos)
• Store beta has been added as an app (not to confuse with Store)
• Maps has been revamped
• Windows Feedback has been revamped
• Sound recorder has been revamped
• Lumia Camera beta has been added as an app
• Xbox has been added as an app (not to confuse with Games)

And further

• The Windows kernel has been updated from version 6.4 to 10.0

Source: Windows Changelog

Posted By: Brink
14 Jan 2015