I'm not entirely sure how I feel about the Old Republic being the setting for the next trilogy. While I'm glad they're going with it I'm scared about what they'll consider canon going forward because as it stands I really like the current, legends continuity we have with KoToR and TOR (I say legends because we're not entirely sure what current Old Republic stuff is even considered canon as of right now). It'll be a huge miss for me if they write out a lot of the currently established characters (like Revan or Vitiate (the Sith Emperor (though he's dead now it'd suck if they completely wrote him out)).
It's pretty much been established that Rey isn't Luke's kid (and it's pretty unlikely Mara is canon anymore though it'd be cool if she was) but I wouldn't be surprised if she is somehow related to the Skywalkers (technically Kylo is a Solo with Skywalker blood so the only living Skywalker we know of is Leia though it's been established her role won't be as big anymore due to Carrie's untimely passing). Then again J.J. could be completely fucking with us and throw a huge curve ball at us. Who knows? With the way these movies have panned out so far there really isn't anything that could surprise me anymore (fuck Palps coming back is honestly par for the course now that Snoke is dead since we have no big baddie to face right now (Bitch Vader will never be anything comparable to Snoke, Palps, of good old Granddaddy Vader)). I was watching a youtube video today speculating that what we heard was actually a holo-recording of Palps that they find on the wreckage of the Death Star which could very well be (using it as a plot point for some sinister plan he was working on in secret before he up and died that Snoke was pursuing and Kylo will maybe finish, who knows).