That behemoth said he was one of the Bendu. And that goes right back to the original Star Wars script, where the Jedi were known as the Jedi Bendu knights. I get the sense that this part of the story might involve Force users who are neither Jedi nor Sith, which certainly seems to open things up a bit. Especially since the Knights of Ren appear to be Force users who are Dark Siders, but not affiliate with the Sith.
Not to go too off topic, but I wonder if Maz Kanata is one of them. She said she's no Jedi, but she knows the Force, and apparently there is a deleted scene where she could wield the Force. I wonder if that is something that will be explored further in the movies.
Back to Rebels, I'm intrigued by the Thrawn angle as well as an introduction to Wedge and some of his backstory. Also like the thought of seeing them steal those Y-wings and the Rebels becoming a stronger force. I wish Filloni would just give up on the Clone Wars crap though! The fact that Maul is still around anfter being cut in half and falling down a bottomless pit gives me hope that we'll see Han Solo in episode 8! I also still can't stand the idea that Rex (one of the most loyal clones and leader of the 501st) is part of the Rebellion! LET THAT CRAP GO INTO THE ASH HEAP WHERE IT BELONGS!