I don't count Kirby as a retcon since her death was supposed to be ambiguous, and it being confirmed she's alive in the sequel immediately after the movie where she almost died works. People like Jennifer have been dead for over 20 years, both in the movie universe and real life. It'd be off-putting at best to just have them suddenly be alive after all this time, as much as I love her.
That said, they can totally bring Parker back as Jennifer's twin sister or something. Same with Sarah/Cici or Samara/Laura.