At the introduction of Keynote in 2003 they said that Keynote presentations would be a XML-based open file format and so, keynote presentations could be created programmatically by 3rd party applications.
Is this still possible in Keynote 6.2?
Until Keynote 6, this was true. However, Keynote 6 uses packages for storing keynotes:
test.key ├── Data ├── Index.zip ├── Metadata │ ├── BuildVersionHistory.plist │ ├── DocumentIdentifier │ └── Properties.plist ├── preview-micro.jpg ├── preview-web.jpg └── preview.jpg
This doesn't stop you from creating older-style XML keynotes, since Keynote 6 is backwards compatible.