It's happened rarely that before the first volume is out that a series is cancelled. I mean if we're to assume that the rank doesn't occur until after eight weeks, and a tankobon has 8-9 chapters in it then it's hard (not impossible I guess) for a series to be cancelled barely one week after being ranked unless it's just doing that badly.Dont series already receive notification of ending before the first volume sometimes even released? Seems a bit too late to wait until then.
In any case, I think I find myself in the group that although is in the age group would prefer series that arent dark and mature in this magazine and such. Based on the recent series that could be grouped as dark, I dont think those that even read this magazine actually would want to read those series in this, at least when looking through recent history. Often as past has shown one can adequately determine the fate of series in just their first chapter.
I think it would be interesting to see if those readers in that age group truly do want dark disturbing mature series in this magazine. I just think they easily have other magazines out there to cater to their needs.
And what other magazines cater to a specific 'darkness'? I always thought that every mag has different series of different genres, but generally do not group them together by one 'theme'. I might be wrong since I'm no expert on Japanese magazines, but from what I see there are 'dark' series in every mag along with series that are 'not dark'. (See how vague that is?) If you mean 'seinen' mags, those are unabashedly not for teens, so I doubt they could simply chuck WSJ and read one of those if they want to see edgy and dark stuff.
Also determining series fates based on first chapters is the same as using tea leaves or tarot cards to determine how to tackle big life decisions. These examples might be old but if you recall, Yu Yu Hakusho's first chapter and it's final arc were really quite different from each other, as is Bleach and several other Shounen. While for the most part a series's first chapter is indicative of what to expect from it, such prediction is not a hard and fast science. So let's just call it what it is. 'Highly amusing guessing.'