It won't be Kylo and Luke. Too much exposition one things that are intentionally sketchy in the film franchise, tbh. I don't see anything like that happening until episode 9 is done, and even then I don't see it being pumped out until a little while after Episode 9 airs. We have what, 3 years until the show could come out at the earliest then?
I don't see it, personally.
I’m curious what people think we will be getting if not a post-RotJ series featuring Luke and perhaps his apprentices. I just can’t envision them making anything else as it will almost certainly have a Jedi as the protagonist and (unfortunately) take place around the films. Disney also seems to be mostly straying away from the prequels so I don’t expect a cartoon around that era, we already have a series set between RotS and ANH, and we can’t really have any Jedi running amok during the GCW. So a post-RotJ seems the most logical choice. And, well, there should be only one Jedi (and some apprentices) around at that point of the timeline.