The reboot was only announced essentially to keep the rights to the F4 movies, because if they hadnt announced it or had a press release regarding them, the rights would have gone straight back to Marvel.
and on the topic of a darker F4, wouldnt that basically defeat the purpose of the F4??? I mean, its not exactly grrity like Bats or Wolverine, its about a fantastic family with awesome super powers, what're they gonna do? have the baxter building replaced with some run down residintial apartment block in the Bronx?!?!