Its a little ways off however the Exchange product team has released some details on what is planned for Exchange 2007 Service Pack 1 (SP1).  They also said they expect to ship a beta version of the service pack on the April installment of TechNet+.

You can read the entire blog posting here:  http://msexchangeteam.com/archive/2007/02/23/435699.aspx

Standby Continuous Replication (SCR)

With Exchange 2007, we introduced Clustered Continuous Replication (CCR) for replication of data between 2 servers within a cluster within the same datacenter. With SCR, data replicates to a non-clustered server in a remote datacenter. If the primary datacenter becomes unavailable, the standby replica in the second datacenter is readily available to be activated.

Mobility

New policies for:

• Enforcing encryption of main memory contents on device
• Enforcing which applications are allowed/blocked from running on the device
• Enforcing networking capabilities: disable wifi, Bluetooth, infrared, external storage
• Enforcing communication capabilities: disable SMS, MMS, POP/IMAP, disable camera

OWA

SP1 will fill in the feature holes that we just didn't have time to complete by RTM:

• Personal distribution lists
• S/MIME
• Rules
• Monthly calendar view
• Deleted items recovery

OWA 2007 SP1 spell checking will add support for:

• Arabic
• Korean

OWA 2007 SP1 will add support for viewing Office 2007 file formats as HTML.

Exchange Management Console

SP1 will fill in the GUI holes that we just didn't have time to complete by RTM, including:

• Public folder configuration
• POP and IMAP configuration
• SendAs permission configuration
• Delegation wizard scenarios

Web Services

New web service coverage will include:

• Public folder access 
• Delegate management
• Folder permission management

IPv6

On Longhorn Server, we will support Exchange 2007 on native IPv6 networks.

Move Mailbox

This vital tool administrator tool has been beefed up to include import and export to a .pst