While I love this comment, it does bring up the point that Jay Leno never wanted to retire, and that some people miss a key point to this story:
NBC and Conan signed a deal back in 2004 that Conan would take over in 2009 weather Leno wanted to retire or not.
NBC and Leno also signed a contract saying that he was going to quit and let Conan take over. Leno publicly announced this on his show, shortly after his 5-year contract renewal.
[ame=http://www.funnyordie.com/videos/6d1caacad1/jay-s-2004-announcement]Here's the actual announcement[/ame] from 2004.