There were some days/times with walk ups this year. I believe that the walk ups were sometimes, if not always, seated in an outside area. The SWW thread (below) may have more anecdotal info for you from this year. Keep in mind, that this is the first year for Rebel Hangar, and it was added really late, like May, so things could be very different next year. Also, I don't know if you knew that this year it is open on weeknights (non-SWW days) as well, like the SWW character meals. There are some hopes, probably just rumors, that it could become permanent. We'll see. I plan on going to SWW next year as well. Hope to see you there.
http://www.disboards.com/threads/official-star-wars-weekends-thread-tips-and-tricks-2015.3324422/