I suggest to deprecate XML serialization package in 3.1 and remove it in 3.2. There were past discussions why it is not a working solution for real life applications (DOM, singletons, etc.). Also real life serialization/deserialization patterns are different from what we provide there (at least I couldn't adopt it to any of my own needs). And finally there's nobody around willing to address these deficiencies.
Some time back I started on an alternative serialization package, currently checked in to sandbox:
It uses XStream and is based on an idea similar to ROP - serialization specification is defined like to prefetches in a select query - there's a root entity, and there's a bunch of prefetch paths for related objects that need to be serialized together with the root objects. It works, but has some of rough edges and missing features. Also would be really cool to port that to JAXB, as JAXB is a part of J2SE these days. As I won't be able to work on this any time soon, it requires other motivated individuals to make it production-ready.
In any event I don't see a point in keeping the existing XML package regardless of the outcome of the replacement, and would like to phase it out.