Fitting all the characters is a bit of a stretch–this is a show that has a list of characters being introduced often, and each of those characters have their own story arc. They may not all be the main characters, but they are just as important.
I agree that it does suck that Emma and Snow White won’t have that much screentime as before, but I am sure the episode will have a good deal of Prince Charming, Henry, and Red Riding Hood. 😀
Also, this show is very much driven by the characters–the characters are one of the most interesting parts of Once Upon A Time. So the writers have to give them all a moment to go through their own history and problems.