It's unlikely that you'd notice this, but with Walter Cronkite's death, CBS considered retiring the voice intro he'd recorded for "The CBS Evening News with Katie Couric," which they'd been using since she took over the anchor chair. Reports today say CBS is going to keep it on the air as sort of an ongoing tribute to Cronkite (until they can figure out something else). NBC did the same thing when Howard Reig -- the staff announcer whose recorded voice introduced "Nightly News" with John Chancellor, Tom Brokaw, and Brian Williams -- died in 2008. He was replaced by Michael Douglas (yes, that Michael Douglas).
When CBS does use another voice, there's no word on whether they'll go the celebrity route or just hire another voice guy (hey, I'm available!!), but it won't have any affect on ratings either way.
Neither will another change that CBS made a week ago, which you also didn't notice. They've retired the "chirp" that the CBS Radio Network used as an automation cue for about 30 years. The state of the art in digital distribution has rendered the chirps obsolete, as explained here [thanks to Joe Crain for the link].
In reading that story, I'm reminded of a classic radio prank pulled by Howard Hoffman and some friends many years ago. At the time, Larry King was doing his overnight radio show for Mutual, which used a cue tone that sounded like "bee-doop." It would tell automation systems at their affiliates when to insert a local commercial, when to rejoin the network, etc.
Howard recorded the "bee-doop," called the show and, once on the air and talking with King, played the "bee-doop" down the line a few times at irregular intervals during the conversation. After about the third time, King asked, "What's that sound?" Howard played dumb, replied "What sound?" and hit it again. Meanwhile, the legend says that not only were the guys in King's control room going crazy, but unmanned affiliates all across the country were firing carts with commercials or other elements, causing havoc on the airwaves.