Though Activision and id Software have had a publishing partnership for quite a while, that is about to change following a recent announcement by the company behind the Doom and RTCW series. John Carmack announced that the company would now be using EA as it's publisher. The announcement, which happened at E3, indicated that id's upcoming title would be published by EA. This adds to EA's already considerable portfolio of companies "under their wing" which they publish for. The rest of 2008 has a veritable horde of titles in the works under them.
While this isn't good for Activision, it isn't a terrible blow. Activision has many large sources of revenue, and id's departure shouldn't affect them much, especially with their recent merger with Vivendi.