I've been searching around and I have found one answer which is "it's in the same universe" so that shows that it could either be a prequel or a sequel.
To piggy back on what @Kaizerwolf has said in the comments above. Outlast 2 is going to be an "Indirect Sequel" that will "take place in the same universe at Outlast, but it will feature different characters and a different setting" According to the Outlast 2 Wikia.
I'm sure more details will be released as the game continues to develop. I hope this helps out :)