Arduino IDE across hardware platforms

My understanding the Arduino is setup mainly for using Atmega88 and Atmega168.
With experimentation with the atmega328p and the advent of Sanguino, is there a plan to integrate those as well as atmega324P, and other dip chips into the Official Arduino IDE. It would be really cool if there were an assortment of hardware platforms that were all cross compatible with the Arduino IDE(and associated bootloaders).

Is this underway and how much of a task would this be?

The current plan is to create an "Add board..." menu item that will install all the files needed to support a board from a single .zip file, including the appropriate core libraries, boards.txt entry, etc. Zach Smith, creator of the Sanguino has volunteered to work on this.