They've only said that jobs would be limited as to what they can cross-class, but not exactly how this would be limited. Thinking about it recently, though, our action bars would be extremely full if they added new abilities on top of our old ones (and Archer would not have any room at all for Bard-exclusive abilities) so I'm thinking they may just be reducing the number of Cross-class slots we get while on Jobs and using those slots for Job skills.