It's been stated in some of the reference books that the Empire is still around in Disney's post-ROTJ, but with pretty much no military and small territory....and yet they're not really brought up in the films at all. It's kind of one of the unanswered questions that even Disney's post-ROTJ books kind of gloss over, it seems, although I think it's implied in "Bloodlines" that some of them support-or even arm the First Order. Basically they still have Moffs and stuff, maybe a totalarian society but no real fleets or Stormtroopers.
With the FO pretty much implied to be conquering the galaxy quickly in TLJ I'm guessing these imperial worlds would also wind up under their flag.
Kind of reminds me a bit of Gundam; after the first series, the civilian government of Zeon forms the somewhat Republic of Zeon, while the military remnant forms the Delaz Fleet, and later Neo-Zeon and Axis. I wonder if Abrams is a Gundam fan; his Star Trek, in which a lot of the senior staff of the Enterprise are incapacitated or killed putting somewhat inexperienced but gifted cadets and civilians in their place, kind of reminds me of Gundam's initial set-up. (Not saying he copied it, just an interesting parallel).