I don't really think its like that.
There seems to be some sort of misunderstanding that dark=emo vampire raven dementia way. Dark has to do with the mood of the story. When you want to tell a certain story to its optimal potential, then certain moods must be evoked. (Though honestly, I think that grim or solemn would be a better word to put the events of chapter 4.)
I started playing Tales with no ideas or exceptions as to what it was going to be about, so I was pleasantly surprised to find that it was playing with certain moods and emotions that weren't tried in the series before.
Some may say that what happened was corny, cheesy, or what ever food related adjective you may want to use, but I found it believable within the realms of the series. (I mean, what's not cheesy about the game's storyline?)
But I digress.
I think that rather than a longing for "dark", we're looking for something new and exciting. Sunshine and happiness has been done, and done well mind you, but if you never at least TRY to explore outside that realm then you'll end up with the Land Before Time series/saga/couldn't care less.
I'm not exactly the best with explaining my thoughts, but I hope you at least get some of the things I said. >_>
I am a dinosaur. BUT! i am hiding.