METS 1.7 is available at http://www.loc.gov/standards/mets/version17/mets.v1-7.xsd
It will replace http://www.loc.gov/standards/mets/mets.xsd in a month if no problems are found.
Change requests for the next version of METS are being collected here
METS 1.7 changes:
Created parType complex type to allow a seq to contain a par.
Created a FILECORE attribute group with MIMETYPE, SIZE, CHECKSUM, CHECKSUMTYPE, CREATED; added to mdType and mdRef so they get the core file attributes
Added PREMIS:OBJECT PREMIS:AGENT PREMIS:RIGHTS PREMIS:EVENT to MDTYPE value enumeration
I have checked the new schema against all the example METS in the registered METS profiles and all the samples validate using the 1.7 schema.