I may be smoking crack but isnt Darth Revan waaaay before ROTJ? KOTOR took place a long time before the movies right?
star wars extended universe got retconned
EU got thrown under the bus because most of the EU material (dozens and dozens of books) took place after RotJ and pretty much covers the entirety of the remaining lives of the original characters. If they wanted to reuse those characters for the sequel trilogy (and they clearly did, even if its going to be for lesser roles) that meant either going with one of the pretty terrible EU series, or clearing the slate to do something unique (and something that has the potential to actually be good)
so not only is there retcon for the possibility of Revan in this sequel trilogy, in a universe of sci-fi *and* magic pretty much anything would be possible, they could easily keep the KOTOR/TOR storylines intact and just make Revan thousands of years old from some sort of stasis/Force-ghost re-manifesting somehow/maybe he's just straight up immortal/reincarnation/who knows.
At any rate, even if Revan isn't in the trilogy, I do hope they do something about the nonsesne of the black and white treatment of the Force in the vast majority of Star Wars material. Revan is far and away one of the most compelling Star Wars characters because he is an anti-hero who blurred the lines of light and dark, mastering all aspects of the Force.