Welcome to the forums! I'm glad to see another person hooked on the Oddworld series!
The yellow Abe faces are just there for decoration, I believe, and when the game is loading. The quintology has not been abandoned, as a matter of fact, Munch's Oddysee will be coming out shortly. Did I answer your questions? If you need anything else, give me a roar, I'm the big winged lizard running around like crazy with a furry lizard man and a mutant Slig/Slog!