Going forward, there are some features I'd like to explore for XOM, post-1.0. In many cases, I'm not sure either how to implement or how to design them (or both). Otherwise, they just don't seem like core functionality. But here's some stuff you may (or may not) see in the future:
Vector functions that operate on every node in a list.
xml:id support
Catalog support
Document subset canonicalization
XML digital signatures
XML encryption