This is a recurring theme from a number of PDC 05 attendees. I think the answer is two fold :
The first one can be found at : http://msdn.microsoft.com/windowsvista/building/workflow/default.aspx?pull=/library/en-us/dnlong/html/WWFIntro.asp#wwfi_topic3
The second is that vNext BizTalk 2004 must be a different beast offering more on top of what now is offered. The designers must be made more friendly (anyone who attended the BizTalk 2004 futres will have seen a glimpse of that), the toolset be increased and the adapter offerings increased. I can see BizTalk 2004 being less engine and more toolset. Hopefully it will just get better, some pointers such as the engine/servers in the RFID offering could maybe be added in as well. Lets hope its all of these.
What I think is true is that the future is looking more and more demanding!!
Must go and rest my head after all this content...