There was sufficient time to formulate a long-term plan.
My estimate, based on 50+ years in broadcast (none of it clearing tables in an NPR coffee-break room) is that the successor will already be doing at least a regional (not just local) show. Because of the uncertainty of when the deal would kick in there are contractual things with that individual's present situation that will keep it from happening immediately.
It can't be allowed to take long, though, or momentum would be lost.
I can think of a few candidates - none of whom are "big names" at the national level TV, radio or print. Don't rule out someone from film. Remember, you never thought Ronald Reagan could be president.
Whoever it is will surprise you.