I want to say Inhumans, but the numbers don't add up.
We would need 4 new characters to complete the Royal Family: Karnak, Gorgon, Triton, and Crystal
Black Bolt is definitely eligible - Redo #1
Lockjaw was released in 2010 - Redo #2
Medusa was made recently as an Animated figure only - Redo #3
This lineup is 90% there, maybe Zach is mistaken in thinking one of the unmade characters was previously released?