He was ubiquitous on their in-house stuff, ads for convention coverage, and so on–basically he was the face of their news division–so were they still broadcasting his face after he died? How fast did they recut their entire ad/promo schedule?
I would only think they used his face for promos for shows where he was featured, like Meet the Press*. It wouldn’t have been hard to drop the promos featuring him from rotation, even on the day he died.
There is still an ad where his face is seen, along with a multitude of other NBC folk, albeit briefly.