So who's leaving? For sitcoms, I suspect Raising Hope, Rules of Engagement, maybe Friends and maybe Anger Management. Friends can be seen on TBS about 37x/week anyways. I don't see Two and a Half Men or Seinfeld going anywhere, anytime soon. 'Men' reruns are still in the top 25 in syndication!
The Simpsons aren't rated because there are no national commercials.