As many readers know, I've been working on the "versioning issue" for a few years now. XML Schema 1.0 didn't leave XML authors as well of as we'd have liked, and I've documented a few workarounds(xml.com article). But the best solution is to fix the problem. And better still, be part of the solution rather than the problem. So I've been putting my time and pen to use on the XML Schema WG, working on versioning.
The Schema WG has just published 2 documents: a new XML Structures 1.1 (http://www.w3.org/TR/xmlschema11-1/) that contains a number of versioning changes, and guide to versioning using XML Schema 1.1(http://www.w3.org/TR/xmlschema-guide2versioning/) (authored by yours truly). I think the guide is a great place to start learning about versioning in xsd 1.1. I hope it motivates XML authors to look closely at XSD 1.1 and give their feedback on the various versioning changes.
The biggest 3 changes in XSD 1.1 for versioning in the current structures draft are:
Weak wildcards - permits wildcards adjacent to optional elements (mostly fixing the dreaded UPA problem)
Updated All Group - wildcards within All Group(so no restrictions to just sequences for extensibility)
Negative wildcard - exclude specific namespaces and names
There's more work being planned, such as:
Fallback To Declared Type - use declared type if xsi:type is unknown
Auto-insertion of wildcards
Not in Schema wildcard - a wildcard that allows anything not defined in the current schema
So take a read and send in some feedback on what you like, don't like!