Due to a feud between Marvel Comics CEO/Chairman Ike Perlmutter and Fox Studios over the film rights to the characters, Perlmutter ordered the cancellation of the Fantastic Four comic and removal of the characters from being involved in various merchandise.
Now for whatever reason - possibly that Marvel Comics and Fox are on good terms again (they're working on the X-Men TV series together) - the Fantastic Four are thought to be returning to the comics.
The latest offering that it might be a possibility is a sketch Alex Ross posted on his Instagram account and then deleted (via reddit), which shows Reed and Sue Richards in new Fantastic Four costumes. We can guess that the artwork might be for an upcoming cover, but that Alex Ross wasn't supposed to release it and posted it accidently.
Maybe Marvel Comics will be announcing the new Fantastic Four next month at the NYCC?
Regarding the feud between Marvel and Fox, Fantastic Four and Secret Wars writer Jonathan Hickman recently confirmed it's real.
"I think it’s pretty common knowledge at this point that Marvel isn’t publishing Fantastic Four because of their disagreement with Fox,” Hickman explained to Newsarama. “While it bums me out, I completely understand because, well, it isn’t like they’re not acting out of cause. Fox needs to do a better job there.”