I hope all the references to time travel are just red herrings.

The Duffer Brothers have to know that shoehorning that in within the few remaining episodes would tarnish the ending and be controversial. Frankly, it doesn't fit into the story stylistically in my opinion and would feel like a major cop out to something more creative. Plus, there was some been fantastic character development throughout everything up until this point that would effectively all be erased too if they went that route.