Just got some extra information about the plans for WCF and WF after the post Silver (which is in the Orcas timeframe) release. Here are two extra ideas that I picked up at the WCF+WF Orcas training. The other ones are mentioned in a previous post.
Currently WF does not have a clear model on which data you can use in which part of the workflow. There are plans to build facilities for that based on the DataContract model, as opposed to the Serializable style of data.
Besides that there are plans to give you data transformations. This will give you the ability to transform one data format into another using a BizTalk mapper style mapping technology. This should be usable from both WCF and WF and outside of these technology stacks as well. This will also be based on the DataContract model.
Note that these are plans, so no guarantees. Also, I couldn’t get preciser details as this is still all very hush-hush.