Dave Itzkoff of the New York Times tweeted that during the Q-and-A warmup of a recent taping of his Late Show, Dave Letterman said they'd invited two more guests to appear before their last show on May 20. One is Jay Leno and the other is Brian Williams.
If that's so, I can't imagine why Leno wouldn't say yes. Presumably, the two of them would spend the segment burying all hatchets and speaking well of each other. I can imagine why Brian Williams wouldn't. It looks like NBC is getting ready to dump him and settle his contract. I doubt that will happen in the next three weeks and until it does, he'd be wise to lay low. But maybe they'll work something out.