Today there is the "boards.txt" file that basically lists the various Arduinos supported. This reflects the distributor (Arduino team) perspective more so than the user perspective.
One possible extension could be a user defined "Boards.txt" that lists MY boards. In this file I envision a reference to a definition within official boards, a default COM port and a descriptive name. So that a selection from this short list of "my boards" would setup the IDE for correct board and com port using a well known name (e.g. My first Arduino on COM3). Users could possibly get some help from the IDE towards creating such a file through a dialog asking: What type of Arduino do you have? - and - What port is it connected to?
Ideally I would also like to see the selection of board/port linked to a project. So that whenever I change/open a new project, the IDE will default to the "most recent" board/port used for uploading that particular project.