On April 24th, I blogged about Microsoft's announcement of BizTalk Server 2006 R3. Today, Microsoft is announcing plans for BizTalk Server 2009, which will replace original plans for the R3 release. You can read Steven Martin's official announcement here: http://blogs.msdn.com/stevemar 
As with BizTalk Server 2006 R3's original list of new features and enhancements, the focus on BizTalk Server 2009 is enhanced platform support, SOA and Web Services, including:
- New web service registry capabilities with support for UDDI (Universal Description Discovery and Integration) version 3.0
- Low-latency messaging enhancements and ESB Guidance
- Enhanced service enablement of applications (through new and enhanced adapters for LOB applications, databases, and legacy/host systems)
- Enhanced service enablement of "edge" devices through BizTalk RFID Mobile
- SOA patterns and best practices guidance to assist our customer's implementations
This announcement, and corresponding (non-comprehensive) feature set is significant in my opinion for two reasons. First, it reflects a continued commitment on behalf of Microsoft Connected Systems Division (CSD) to the BizTalk Server platform. This is important for businesses and developers who have made significant investments in BizTalk Server and are looking beyond the next 3 to 5 year horizon in making strategic architectural decisions that will have a lasting effect.
Second, it reflects an emergent approach to simplifying application integration, SOA enablement and adoption which ensures that by staying up the date and following platform patterns and best practices, a gradual yet consistent readiness for upcoming technologies and platform enhancements is provided.
I believe that BTS 2009 will be a step forward in lubricating the adoption of more model-driven technologies through a stronger, more connected alignment with the .NET Framework, Windows Communication Foundation and Windows Workflow.I have talked a bit about the Connected Systems Technology curve here.
To summarize, The .NET Framework cross cuts the entire Microsoft stack, from the user interface to the database, and this is certainly true within Windows Communication Foundation, Windows Workflow Foundation and BizTalk Server. However, moving from pure .NET to WCF is non-trivial because it requires an 
evolution in thinking beyond traditional development and into contract-first development and SOA. In my career, I recall the struggle I had in moving from writing procedural code to thinking in terms of object orientation, and I don’t have to look too far back to remember the shift in thinking in moving from white-box-reuse-based objects to black-box component programming. While the WCF developer likely has a system/middle-tier background, the evolution to workflow and modeling will prove just as challenging because strong .NET system developers tend to be much more comfortable working imperatively. BizTalk developers, on the other hand, have been benefiting from the maturity in tools, modeling of workflow and message-based communication for several years. For the BizTalk developer and architect, the transition to WCF, and especially WF is nearly seamless because with the fundamentals in place, the declarative and model-based design experience that WCF and WF introduce respectively become second nature and so does the rate of adoption.
While there has been no official change to release plans, a CTP update is planned for Q4 of CY08. Microsoft will use this broad feedback from customers and partners to help us validate the features and readiness of the product.