Rather's career was scheduled to end this coming Spring anyway. He's had a 2005 retirement planned for a while.
Question is, will this now lead him to quit six months early? All signs point to no. His exit will be pretty smeared, however. I can see him pushing retirement back a couple of years to re-establish credibility, and maybe to root for Hillary in '08, but he's not going anywhere because of the memos.
The nicest thing we can do for Dan Rather is give him a Happy Retirement party on Nov 2nd with a Bush victory.