Okay, so here's what I HAVE figured out for each animation studio in the eighties so far.
Disney
They will continue to do television shows and live-action films throughout most of the decade, and this will also be when their classics will be released on home video. I imagine close to the end of the decade, they will make a theatrical film based on either Uncle Scrooge or Winnie the Pooh.
I'm still debating whether they will start doing the infamous Mickey Mouse Act or not. I can see them being totally fine with letting Mickey fall into the public domain (since he was a bland character anyway, and the only reason he became popular was because Walt kept trying to push him into the public's eye when he was alive), and maybe accepting a different character like Winnie the Pooh as their new mascot instead. Alternatively, they could make it so that the original "classic" Mickey with the dot eyes is public domain, but the current Mickey is still under copyright. (Like how Thor from Norse mythology is public domain, but Marvel Thor is under copyright.)
Warner Brothers
Chuck Jones will do Little Nemo: Adventures in Slumberland, and maybe one other film. Who Framed Roger Rabbit will still be released, but it will be a WB film instead of a Disney film. Steven Spielberg will join WB's animation department after that.
Fox
Fox Animation will continue to release animated films directed by Don Bluth, both the ones from OTL like The Secret of NIMH, and the ones done by Disney IOTL like The Little Mermaid and Beauty and the Beast. They will also release Dragon's Lair and Space Ace, and those games will be such hits that virtually every animation studio will want to do interactive movie games as well.
Fleischer
Ralph Bakshi will decide to try his hand at "FAMILY pictures", and will first release Wizards, then will do two Dr. Seuss adaptations: The Lorax and The Butter Battle Book. (Seuss went back to children's books after leaving Warner Brothers, and I imagine Bakshi was a fan of the films written by Seuss at WB.) Paramount still owns the rights to DC, so Bakshi will direct 1989's Batman instead of Tim Burton.
Bakshi will also produce the Star Trek reboot series The Next Generation. Meanwhile, John Kricfalusi, Danny Antonucci, and maybe other notable cartoonists will join Fleischer at this point, and make their own animated series.
IOTL, Donkey Kong started out as a Popeye game before Nintendo lost the rights...so maybe Paramount could let them keep the rights ITTL, resulting in the Mario franchise being butterflied away.
Pixar
John Lasseter will leave Fox Animation and direct The Brave Little Toaster as a CGI film. (Maybe Disney will help produce it, and this will be what rekindles their interest in animated films.)
Tim Burton
He and Henry Selick will do The Nightmare Before Christmas as a TV special instead of a feature. Haven't figured out whether it should be stop-motion or hand-drawn. (I heard Burton IOTL gained his love of stop-motion from the Rankin-Bass specials, but those have been butterflied. Of course, he could just as easily gain this interest from the Ray Harryhausen films.) Once again, maybe Disney will produce it. (I also had the idea of him and Selick teaming up with John Lasseter and the Pixar team, and experimenting with CGI/stop-motion hybrids, which The Brave Little Toaster could end up being. Since Joe Ranft worked with both Pixar and Henry Selick, it's not as unlikely as you may think.)
MGM
The Plague Dogs will be their first animated film of the decade, then they'll probably do features and TV specials based on their television characters like Yogi Bear, The Flintstones, and Scooby-Doo.
Universal
Walter Lantz's studio will mainly do adaptations of children's books (including obscure ones like Willy Visits the Square World and The Last of the Really Great Whangdoodles, along with maybe a Curious George movie). Haven't figured out who will take over the studio after he passes in the nineties. Some ideas include Phil Roman, Phil Nibbelink, and Phil Kirschner (yes, three Phils).
Rankin-Bass
Will continue to do Peanuts specials, along with Garfield specials and maybe even a Calvin and Hobbes special if Bill Watterson is slightly less reluctant here. IOTL, Bill Melendez handed the Garfield specials to Phil Roman so he could focus more on Peanuts. Maybe ITTL, something like that will happen here...maybe Klasky-Csupo could do Garfield once RB is done with them?
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Any other suggestions?