I don't think you're going to get another Hawking. His story is hard to match because the guy basically shrugged off ALS and flourished for 50 years. The MC Hawking jokes are funny because they're true.

But while I think the people like Nye and Tyson are important, someone more in Hawking's mold needs to be a genuinely novel contributor. I'd put Leonard Susskind's name in the hat.