TYPO3 6.2 LTS switched to namespaces for ViewHelpers but some were missing in the XSD schema and in online documentation. We've corrected this and updated the schema files.
Our generated XSD files from schemaker had some missing Fluid ViewHelpers like f:form.button because we didn't use namespace for the generation and were only catching classes with an entry in ClassAliasMap. Now we changed the generation which means there is a new xmlns
This only affects fluid and IDE integration.
This could result in missing auto-complete in your IDE until you update your editor's configured XSD-to-namespace mappings so it is something to keep in mind the next time you start a fresh project or if you use automatically downloaded schema files.
The FluidTYPO3 team