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One set of goals for DFDL v2.0 will be to advance the state-of-the-art, and describe data formats that none of the prior-generation ad-hoc product-specific data tools have been able to address effectively.

The DFDL Workgroup of the Open Grid Forum also has been saving some issues targeted at DFDL 2.0. 

Recursion

One of the first things people want to model in DFDL always seems to be a binary legacy document formats like RTF or older MS Word documents. These have recursive structures where a section can contain text and other sections. DFDL v1.0 was not designed with document formats in mind, but rather with more traditional "data sets" or files of data in mind.

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And... exactly the same thing for groups and group references. We don't allow these to be annotated currently. We should.

Separate LengthKind for Simple and Complex Types

Very often one wants dfdl:lengthKind='delimited' or dfdl:lengthKind='explicit' for simple types, but dfdl:lengthKind="implicit" for complex types. Separating the dfdl:lengthKind into two properties, or having the ability to specify either way, would simplify many schemas that otherwise have a error-prone need to have a dfdl:ref='complex' format reference on every element of complex type to override the default dfdl:lengthKind. That or you have to split the schema and put all simple types in one file (and use only those simple types), and all complex types in another.