Gliffy documents need to be able to have more than one page. This would be similar to the functionality of worksheets in an excel document.
The concept of a single 'project' document that contains multiple diagrams is the intent.
It will make it easier to collaborate on multiple related drawings (for example, a set of wireframe screen designs). Currently, users have to invite the collaborators to each separate file, and it's difficult to switch among them while editing.