Although COGNOS states they will keep supporting their other products, it is obvious to anyone who has used Reportnet that it is designed to replace Impromtu,Access manager,Designer,Query and Upfront......all in a much more managable environment that greatly extends its capabilities.
Impromtu was always an "in-between" product...to much for casual report builders and not enough for heavy duty report builders....that is now split into 2 products Query studio (easy for just about anyone) and Report Studio (great for building just about anything you can imagine)
The catalog building part of Impromtu is replaced with Framework manager, which builds frameworks (similar to catelogs) in a graphical environment for Query studio users and Report studio users. It also exports the frameworks in iqd format for Transformer/Powerplay (although I would bet that soon Transformer will read frameworks directly.
Framework manger also allows for much greater number of datasources (multi database too) including xml as a datasource. In fact, Frameworks themselves are stored as xml and i've created Frameworks that report on other Frameworks (kinda cool) as well as web services.
There is a lot to Reportnet, with a lot of still undiscovered uses, and it is obvious that COGNOS have created a product that they can add a wealth of functionality to.