Apparently this is something that the Blair Witch creators Eduardo Sanchez and Daniel Myrick are currently working on. Here is what Sanchez had to say on the subject:
"Ideally, each Blair Witch film would be a completely different kind of movie. We've thought about doing a film that takes place in the late 1700s and looks like a [Stanley] Kubrick movie with gritty looking people and lighting. But now, we're thinking about going back and and seeing what happened directly after the first film finished. I think it will have some kind of video element in it, but it won't be a first person hand-held movie."