When James Wan went off to make Fast & Furious 7 we all wondered if his horror movie days were behind him. Apparently not, as he's signed on to return for The Conjuring 2, which recently got bumped from October 2015 to TBD 2016. The return of the filmmaker is probably why the delay happened.
I've heard it's unlikely that Wan will want to return for Fast 8 - rumor has it the experience wasn't quite what he expected - even though Universal has an option on him for more sequels. At any rate, they let him make this movie his next film, which definitely indicates to me someone else is coming on for Fast 8.
The sequel will be written by original writers Chad and Carey Hayes, and it's going to a "Further Adventures of Ed and Lorraine Warren" type of movie - which I'm all for. I really disliked Annabelle, which Wan did not direct, and am happy to see this franchise go into more interesting places. And by the way, that extra time between Annabelle and The Conjuring 2 allows the audience to forget how much that doll movie stunk.
Wan also signed an overall production deal with New Line, which sets him up in-house to make a whole bunch of horror, scifi and comedy movies. It's a strong deal for everybody involved, and it should give Wan plenty of room to keep churning out his crowd-pleasing horror movies.