Steef-Jan has a great post about the next release of BizTalk Server in his blog. It seems to be mostly a platform upgrade, but the improvements in the area of Azure integration, and the new features of Azure in IaaS specifically (persistent VM’s + VPN support) open up interesting possibilities for BizTalk usage.
[Edit] Kent Weare also has an interesting post on this topic, based on a presentation at TechEd US (I think).