I have heard that all of these features will be available for the 798 units.
The 788 units do not have Si sonar capability so they will not get the Down Imaging capability but should get all of the rest. In there was a software update for the 788c units (not 788ci or the NVB versions) released to the Humminbird web site last Friday that added the improved GPS/Chart response, LakeMaster card capability and the new 2D sonar color palettes.