The latest beta version of BizTalk 2006 R2 is quite stable so Microsoft should meet its target release date later this summer. This upgrade has some pretty cool new functionality that make BizTalk an even more complete and compelling solution for the Enterprise. Amongst these new features are a more complete set of functionality to support EDI and AS2. While EDI is now an ancient technology, it is still very popular for large companies that need to exchange orders and such. However, they are gradually moving their EDI infrastructure off of the archaic VAN networks and unto the Internet. This is where support for the AS2 standard comes in handy. Note that BizTalk will not support VANs out of the box, but I don't see that as a big limitation.
Another interesting new set of functionality is brought about by the inclusion of Microsoft's RFID infrastructure. RFID is finally coming of age and it will be a huge force in the market for the foreseeable future. The fact that BizTalk will provide complete support for designing high performance RFID systems bodes really well for the future of the product.
Another major change in R2 is the introduction of a new adapter framework built on top of Windows Communication Foundation. This is pretty exciting news for two reasons. First, it means a new and much more powerful and flexible way to build adapters for BizTalk. But the second reason actually has nothing to do with BizTalk: the new adapter framework and the adapters that will be built for it are going to be reusable outside of the BizTalk platform. So other products like MOSS and K2 will be able to leverage these adapters. I also think that we will see an explosion in the number and quality of adapters becoming available, along with lower prices.
Ala-in-all, even though R2 doesn't get a full version name upgrade, I do believe that it is a very significant update, and it should accelerate the adoption of BizTalk in the Enterprise.