I'm not aware of anyone who can replace him perfectly. There are a set of people who overlap a bit and remind me of Sagan in different ways. Neil DG Tyson. Bill Nye. Richard Dawkins. Elon Musk.

Neil deGrasse Tyson and Brian Cox (not NASA, of course) have been doing a great job, and things will only get better, with more discoveries, and better ways of communicating those discoveries.

I take you missed the "Cosmos, a time-space odyssey" series last year?