Today, Microsoft and Citrix announced a comprehensive joint promotion for Virtual Desktops, enabling mainstream adoption of desktop virtualization adoption.
This new strategy will extend the desktop virtualization technology collaboration between Microsoft and Citrix with a joint collaboration agreement. One of those extensions are new integrations with the Microsoft platform in XenDesktop 4 Feature Pack 1.
One of the key changes that Microsoft does, is to it’s licensing for virtual desktops program. Also Microsoft and Citrix is determined to together delivering the best VDI solution in the market.

There are 3 key elements to the Citrix XenDesktop and Microsoft Virtual Desktop Infrastructure Standard Suite:

1. Simplified Microsoft licensing
2. Joint offers to get customers started
3. Joint Collaboration Agreement

Introducing Windows Virtual Desktop access (Windows VDA)

Microsoft is constantly looking at ways to improve their licensing for virtual desktops. In response to feedback received from their customers and partners, Microsoft is announcing changes to the way customers license Windows for use in virtual environments using the VECD licenses. 
The Windows VDA will have the following:

• License your Windows VM for access from thin clients, third party, and non-Windows-based devices
• A device-based subscription
• $100/year/device
• Primary user has extended roaming rights
• Software Assurance benefits for Windows

The following changes take effect on July 1st 2010:

• Windows VECD and Windows VECD for SA will no longer exist on the pricelist.
  • Customers that use PCs already covered with Windows Client SA to access a virtual desktop do not need any additional licensing. Virtual desktop access rights have now been bundled into Windows client SA, thereby further increasing the value of SA.
• For customers that intend on using devices that do not qualify for Windows client SA (such as thin clients, third party contractor PCs, etc), Microsoft is introducing a new license called Windows Virtual Desktop Access (Windows VDA). Windows VDA is a device based subscription that retails at $100/year/device, and is available through all major Microsoft Volume Licensing programs such as EA, Open, Select and Open Value. Windows VDA includes the following benefits:
• Rights to install and use Windows desktops in the datacenter.
• Extends Windows client SA benefits to virtual desktops, such as 24*7 support, training vouchers, etc.
• Ability to access upto 4 virtual machines concurrently.
• Extended roaming rights enable the primary use of a windows VDA device to access their virtual desktop from any device outside of the corporate network, including internet cafés and home PCs.
• Upgrade / downgrade rights for Windows, giving customers the option to use any version of Windows, including the Enterprise editions of the software.
• Independent of the number and location of virtual machines, ie, virtual desktops can be installed and moved across any combination of servers and storage.
• Microsoft Office use rights will also be updated to enable the use of Office for specific VDI scenarios, such as the ability for the primary user of a Windows VDA device to access their licensed copy of Microsoft Office from non-corporate PCs, such as internet cafés and home PCs.

Another part of the joint Collaboration Agreement announced today, is the introduction of Microsoft RemoteFX(former Calista)
The Microsoft RemoteFX platform in Windows Server 2008 R2 SP1 enables a local-like, rich experience for session-based or virtual desktops.

Here are some resources to read up on:

Microsoft Accelerates Desktop Virtualization

Microsoft to simplify VECD and partnering with Citrix to bring RemoteFX (formerly known as Calista) to HDX

https://www.desktopvirtualizationhour.com/