Pretty much what The King of the Monsters said. Little Godzilla still exists as a prototype, and he was unveiled last year, the same time King Caesar was. Caesar got his release a few months later, and from what I understand, Little Godzilla is still moving towards production. I believe we will see it next year, after the newest wave of Bandai Creation figures, which includes re-releases of Godzilla 1954 and GMK King Ghidorah (as well as the forthcoming Godzilla 2014) does its rounds.
As for the Tokyo Vinyl King GHidorah and Minilla, its unlikely we will ever see those at this point. The Godzilla and Showa Mechagodzilla figures didn't sell well at all, and still arent selling. Chances are you've seen four or five of them piled up at Toys R Us', unsold and taking up space. Personally, I like the Tokyo Vinyl figures, and that King Ghidorah looks SICK! But as long as the first two releases continue to sell poorly, releasing them would be a risky for Bandai.
But Little Godzilla? I'm positive he will come out eventually! Lets hope he doesn't go the way of Anguirus '55 and Mecha-King Ghidorah... which also really need to be released!